class 10 Hydrogen chloride

Chapter 8

Study of Compounds — Hydrogen Chloride

Class 10 - Concise Chemistry Selina

Exercise 8 — Multiple Choice Type

Question 1

Hydrogen chloride molecule is:

1. Polar covalent

2. Non polar

3. Ionic

4. Co-ordinate

Answer

Polar covalent

Reason — Hydrogen chloride (HCl) is a polar covalent molecule because it is formed by sharing of electrons between hydrogen and chlorine atoms. However, chlorine is more electronegative than hydrogen, so it pulls the shared electrons closer to itself. This creates a partial negative charge on chlorine and a partial positive charge on hydrogen, making the molecule polar.

Question 2

Hydrogen chloride gas being highly soluble in water is dried by

1. Anhydrous calcium chloride

2. Phosphorous pentoxide

3. Quicklime

4. Conc. sulphuric acid

Answer

Conc. sulphuric acid.

Reason — Drying agent used for drying should only remove the moisture and not react with it, hence, conc. sulphuric acid is used as the drying agent.

Question 3

The aim of the Fountain experiment is to prove that:

1. HCl turns blue litmus red

2. HCl is denser than air

3. HCl is highly soluble in water

4. HCl fumes in moist air

Answer

HCl is highly soluble in water

Reason — Fountain experiment is performed to show the great solubility of HCl gas in water.

Question 4

HCl dissolves in toluene (C₆H₅CH₃) and the solution:

P — contains hydronium ions.

Q — can produce carbon dioxide on reacting with sodium carbonate.

R — does not show any acidic property.

Which of the following holds true?

1. Only P

2. Only Q

3. Only R

4. Both P and Q

Answer

Only R

Reason — Toluene is an organic solvent and non-polar in nature. When HCl dissolves in toluene, it does not ionize to form hydronium [H₃O⁺] ions. Since there are no free hydrogen ions, the solution does not show acidic properties and also cannot react with sodium carbonate to release carbon dioxide gas. Therefore, only R is correct — the solution does not show any acidic property. b

Question 5

Assertion (A): HCl is produced by the reaction of hydrogen and chlorine in diffused sunlight.

Reason (R): This reaction is explosive in sunlight.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true but R is not the correct explanation of A.

3. A is true but R is false.

4. A is false but R is true.

Answer

Both A and R are true and R is the correct explanation of A.

Explanation— HCl is produced, when moist hydrogen gas combines with chlorine in presence of diffused sunlight. Hence, assertion (A) is true.

H2+Cl2→sunlightdiffused2HClH2​+Cl2​diffusedsunlight​2HCl

The formation HCl is a explosive reaction in direct sunlight but it is negligible in dark. So, it is carried out in diffused sunlight. Hence, reason (R) is true.

Therefore, Reason (R) thus provides a valid explanation for why this reaction is occurring in diffused sunlight. Hence, Reason (R) is the correct explanation of assertion

Question 6

Assertion (A): The Fountain experiment is used to demonstrate the high solubility of HCl gas.

Reason (R): Red litmus solution turns blue in Fountain experiment.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true but R is not the correct explanation of A.

3. A is true but R is false.

4. A is false but R is true.

Answer

A is true but R is false.

Explanation— The principle of fountain experiment is to show the great solubility of the HCl gas. Hence the assertion (A) is true.

The blue litmus solution turns red due to the acidic nature of hydrogen chloride gas in the Fountain experiment. Hence reason (R) is false.

Question 7

Assertion (A): HCl gas is collected by downward delivery.

Reason (R): HCl gas is heavier than air.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true but R is not the correct explanation of A.

3. A is true but R is false.

4. A is false but R is true.

Answer

Both A and R are true and R is the correct explanation of A.

Explanation— Hydrogen chloride gas is collected by the downward delivery (upward displacement of air). Hence, the assertion (A) is true.HCl is collected by downward delivery because it is 1.28 times heavier than air. Hence, reason (R) is true and it is the correct explanation of assertion (A).

Question 8

Assertion (A): HCl gas fumes in moist air.

Reason (R): HCl gas is highly soluble.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true but R is not the correct explanation of A.

3. A is true but R is false.

4. A is false but R is true.

Answer

Both A and R are true and R is the correct explanation of A.

Explanation— Hydrogen chloride (HCl) gas fumes in moist air because it is highly soluble in water. In the presence of moisture, HCl gas dissolves in water vapour in the air to form tiny droplets of hydrochloric acid, which appear as white fumes. So, both the assertion and the reason are true, and the reason correctly explains the assertion.

Question 9

Assertion (A): HCl gas dissolves in water as well as organic compounds like toluene.

Reason (R): HCl is a polar covalent compound.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true but R is not the correct explanation of A.

3. A is true but R is false.

4. A is false but R is true.

Answer

Both A and R are true and R is the correct explanation of A.

Explanation— Hydrogen chloride (HCl) is a polar covalent compound, which means it can dissolve in polar solvents like water due to attraction between opposite charges. Interestingly, it can also physically dissolve in some non-polar organic solvents like toluene, but without ionizing. The reason HCl can dissolve in both is due to its polar covalent nature. Hence, both the Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 10

Assertion (A): HCl gas is used in the preparation of chlorine and chlorides.

Reason (R): Lead chloride is not produced from HCl.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true but R is not the correct explanation of A.

3. A is true but R is false.

4. A is false but R is true.

Answer

A is true but R is false.

Explanation— HCl gas dissociates into hydrogen and chlorine, when heated to 500°C and hydrogen chloride reacts with metals that come before hydrogen in the electrochemical series to form corresponding chlorides of those metals. Hence, assertion (A) is true.When concentrated Hydrochloric acid is oxidised by strong oxidising agent like lead oxide lead chloride is formed. Hence, reason (R) is false.

Pb₃O₄ + 8HCl (conc.) ⟶ 3PbCl₂ + 4H₂O + Cl₂ ↑

Question 11

Assertion (A): HCl has sour taste.

Reason (R): HCl is highly soluble in water.

1. Both A and R are true and R is the correct explanation of A.

2. Both A and R are true but R is not the correct explanation of A.

3. A is true but R is false.

4. A is false but R is true.

Answer

Both A and R are true but R is not the correct explanation of A.

Explanation— Hydrogen chloride has sour (acidic) taste. Hence, the assertion (A) is true.HCl is highly soluble in water and it can be proved by performing Fountain experiment. Hence, the reason (R) is true.

However, the high solubility of HCl in water doesn't relate to its taste, Hence, the reason (R) is not the correct explanation of assertion (A).

Exercise 8 — Very Short Answer Type

Question 1

Fill in the blank from the choices in the bracket :

(a) Quicklime is not used to dry HCl gas because CaO is ............... [alkaline/acidic/neutral]

(b) When sodium chloride is heated with concentrated sulphuric acid below 200°C, one of the product formed is ............... (sodium hydrogen sulphate / sodium sulphate / chlorine).

Answer

(a) Quicklime is not used to dry HCl gas because CaO is alkaline.

(b) When sodium chloride is heated with concentrated sulphuric acid below 200°C, one of the product formed is sodium hydrogen sulphate.

Question 2

Name :

(a) a black metallic oxide which reacts with hydrochloric acid to give a coloured solution.

(b) two colourless gases, which when mixed produce a white solid

(c) two gases which chemically combine to form a liquid.

(d) a chloride which is soluble in excess of ammonium hydroxide.

(e) the chemical in which gold can be dissolved.

(f) the experiment which demonstrates that hydrogen chloride is soluble in water.

(g) the gas produced when chlorine water is exposed to sunlight.

(h) the acid which on mixing with silver nitrate solution produces a white precipitate which is soluble in excess of ammonium hydroxide.

(i) the gas which produces dense white fumes with ammonia gas.

(j) an element which reacts with hydrogen to form compound which is strongly acidic in water.

Answer

(a) Copper oxide (CuO)

(b) Hydrogen chloride and Ammonia

(c) Hydrogen and Oxygen

(d) Silver chloride

(e) Aqua Regia

(f) Fountain experiment

(g) Oxygen gas

(h) Dilute hydrochloric acid

(i) Hydrogen chloride

(j) Chlorine

Explanation

(a) Copper oxide (CuO) is black, reacts with HCl to form blue-coloured copper(II) chloride solution.CuO + 2HCl ⟶ CuCl₂ + H₂O

(b) NH₃ (g) + HCl (g) ⟶ NH₄Cl (white solid)

(c) 2H₂ (g) + O₂ (g) ⟶ 2H₂O (liquid water)

(d) AgCl dissolves in excess NH₄OH due to formation of [Ag(NH₃)₂]⁺ complex.AgCl + 2NH₄OH ⟶ [Ag(NH₃)₂]⁺Cl^- + 2H₂O

(e) Aqua regia (1 part of conc. HNO₃ and 3 parts of conc. HCl) dissolves gold.

(f) Fountain experiment vividly shows HCl gas dissolving in water, creating a fountain effect due to pressure drop.

(g) When chlorine water is exposed to sunlight, chlorine reacts with water to form hypochlorous acid. This acid then breaks apart to give nascent oxygen (O) and hydrochloric acid (HCl). The nascent oxygen combines to form Oxygen gas:Cl₂ + H₂ →sunlightsunlight​ HClO + HClHClO →sunlightsunlight​ HCl + [O] (nascent oxygen)[O] + [O] ⟶ O₂

(h) AgNO₃ + HCl ⟶ AgCl (white ppt.) + HNO₃ which dissolves in excess NH₄OH.

(i) NH₃ [g] + HCl [g] ⟶ NH₄Cl [s]

(j) H₂ + Cl₂ ⟶ 2HCl; HCl is strongly acidic in water.

Question 3

Identify the gas evolved when :

(i) Potassium sulphite is treated with dilute hydrochloric acid.

(ii) Concentrated hydrochloric acid is made to react with manganese dioxide.

Answer

(i) Sulphur dioxide gas

(ii) Chlorine gasMnO2+4HCl→ΔMnCl2+2H2O+Cl2MnO2​+4HClΔ​MnCl2​+2H2​O+Cl2​ ↑

Question 4

Solution A reacts with an acid B (which gives greenish yellow gas on reacting with oxidising agents like Pb₃O₄) to give white precipitate C insoluble in nitric acid but soluble in ammonium hydroxide. Name A, B and C.

Answer

A → Silver nitrateB → Hydrochloric acidC → Silver chloride

Explanation — Solution A is silver nitrate which reacts with acid B i.e., Hydrochloric acid to give a white precipitate C of AgCl which is insoluble in nitric acid but soluble in ammonium hydroxide.

AgNO₃ + HCl ⟶ AgCl ↓ + HNO₃

AgNO₃ + HNO₃ ⟶ no reaction

AgCl + 2NH₄OH ⟶ [Ag(NH₃)₂Cl)] + 2H₂O

Exercise 8 — Short Answer Type

Question 1

A solution of hydrogen chloride in water is prepared.

The following substances are added to separate portions of the solution:

S. No.	Substances added	Gas evolved	Odour
1	Calcium carbonate
2	Magnesium ribbon
3	Manganese(IV) oxide with heating
4	Sodium sulphide

Complete the table by writing the gas evolved in case and it's odour.

Answer

S. No.	Substances added	Gas evolved	Odour
1	Calcium carbonate	CO2	odourless
2	Magnesium ribbon	H2	odourless
3	Manganese(IV) oxide with heating	Cl2	Pungent smell
4	Sodium sulphide	H2S	Rotten egg smell

Question 2

Complete and balance the following reactions, state whether dilute or conc. acid is used.

(a) NH₄OH + HCl ⟶

(b) NaHSO₃ + HCl ⟶

(c) Pb(NO₃)₂ + HCl ⟶

(d) Pb₃O₄ + HCl ⟶

Answer

(a) NH₄OH + HCl (dil.)⟶ NH₄Cl + H₂O

(b) NaHSO₃ + HCl (dil.) ⟶ NaCl + H₂O + SO₂

(c) Pb(NO₃)₂ + 2HCl (dil.) ⟶ PbCl₂+ 2HNO₃

(d) Pb₃O₄ + 8HCl (conc.) ⟶ 3PbCl₂ + 4H₂O + Cl₂ ↑

Question 3

State the composition of aqua regia. State which component is the oxidizing agent in aqua regia.

Answer

Aqua regia : 1 part of conc. HNO₃ and 3 parts of conc. HCl

Nitric acid present in aqua regia oxidizes HCl to chlorine.

Question 4

How will the action of dilute hydrochloric acid enable you to distinguish between the following?

(a) Sodium carbonate and sodium sulphite

(b) Sodium thiosulphate and sodium sulphite.

Answer

(a) When Sodium carbonate is treated with dil. HCl, odourless carbon dioxide gas is produced.

Na₂CO₃ + 2HCl ⟶ 2NaCl + H₂O + CO₂ ↑

However, when sodium sulphite is treated with dil.HCl, sulphur dioxide gas with a suffocating odour (burning smell) is produced.

Na₂SO₃ + 2HCl ⟶ 2NaCl + H₂O + SO₂ ↑

(b) When sodium thiosulphate is treated with dil. HCl it produces sulphur dioxide gas and yellow sulphur precipitates.

Na₂S₂O₃ + 2HCl ⟶ 2NaCl + S + H₂O + SO₂ ↑

However, S is not produced when sodium sulphite is treated with dil.HCl.

Na₂SO₃ + 2HCl ⟶ 2NaCl + H₂O + SO₂ ↑

Question 5

MnO₂, PbO₂ and red lead react with conc. HCl acid liberates Cl₂.

What is the common property being shown by these metal oxides?

Answer

It shows that hydrochloric acid (HCl) is oxidized to chlorine (Cl₂) by strong oxidizing agents such as MnO₂, PbO₂ and red lead.

Question 6

Write an equation for the reactions of hydrochloric acid on :

(a) silver nitrate solution

(b) magnesium foil

(c) caustic soda solution

(d) zinc carbonate

(e) manganese (IV) oxide

(f) copper oxide

Answer

(a) Silver nitrate solutionAgNO₃ + HCl ⟶ AgCl (white ppt.) + HNO₃

(b) Magnesium foilMg + 2HCl ⟶ MgCl₂ + H₂

(c) Caustic soda solutionNaOH + HCl ⟶ NaCl + H₂O

(d) Zinc carbonateZnCO₃ + 2HCl [dil.] ⟶ ZnCl₂ + H₂O + CO₂ [g.]

(e) Manganese (IV) oxideMnO2+4HClConc.→ΔMnCl2+2H2O+Cl2MnO2​+Conc.4HCl​Δ​MnCl2​+2H2​O+Cl2​ ↑

(f) Copper oxideCuO + 2HCl ⟶ CuCl₂ + H₂O.

Question 7

Write the balanced equations for the reaction of dilute hydrochloric acid with each of the following:

(a) Iron

(b) Sodium hydrogen carbonate

(c) Iron (II) sulphide

(d) magnesium sulphite

Answer

The balanced equation are :

(a) IronFe + 2HCl (dil.) ⟶ FeCl₂ + H₂ ↑

(b) Sodium hydrogen carbonateNaHCO₃ + HCl ⟶ NaCl + H₂O + CO₂ ↑

(c) Iron (II) sulphideFeS + 2HCl ⟶ FeCl₂ + H₂S ↑

(d) Magnesium sulphiteMgSO₃ + 2HCl ⟶ MgCl₂ + H₂O + SO₂ ↑

Question 8

How would you distinguish between dilute HCl and dilute HNO₃, by addition of only one solution.

Answer

When silver nitrate soln. is added to dil. HCl, curdy white ppt. of silver chloride is formed whereas, there is no reaction when silver nitrate soln. is added to dil. HNO₃.

AgNO₃ + HCl ⟶ AgCl (white ppt.) + HNO₃

AgNO₃ + HNO₃ ⟶ no reaction

Question 9

State one appropriate observation when :

(a) Copper sulphide is treated with dilute hydrochloric acid.

(b) A few drops of dil. HCl are added to AgNO₃ solution. followed by addition of NH₄OH solution.

(c) Lead nitrate solution is mixed with dilute hydrochloric acid and heated.

(d) A small piece of zinc is added to dilute hydrochloric acid.

(e) Dilute HCl is added to sodium carbonate crystals.

(f) Concentrated HCl is added to manganese dioxide.

Answer

(a) A colourless gas having smell of rotten eggs is given off. The gas evolved is H₂SCuS + 2HCl ⟶ CuCl₂ + H₂S ↑

(b) Curdy white precipitate of silver chloride [AgCl] is obtained, which is soluble in excess of NH₄OH.AgNO₃ + HCl ⟶ AgCl ↓ + HNO₃AgCl + 2NH₄OH ⟶ [Ag(NH₃)₂Cl)] + 2H₂O

(c) White precipitate of PbCl₂ is formed which is soluble in hot water.Pb(NO₃)₂ + 2HCl ⟶ PbCl₂ ↓ + 2HNO₃

(d) Hydrogen gas is evolved with bubbles and it burns with a pop soundZn + 2HCl ⟶ ZnCl₂ + H₂ ↑

(e) Effervescence of CO₂ seen which turns lime water milky.Na₂CO₃ + 2HCl ⟶ 2NaCl + H₂O + CO₂ ↑

(f) When concentrated hydrochloric acid is added to manganese dioxide (MnO₂), a greenish-yellow gas (chlorine gas) is evolved with effervescence.MnO₂ + 4HCl (conc.) →ΔΔ​ MnCl₂ + 2H₂O + Cl₂↑

Question 10

Write balanced chemical equations for the following :

(a) Sodium thiosulphate is reacted with dilute hydrochloric acid.

(b) Calcium bicarbonate reacts with dilute hydrochloric acid.

(c) Conc. hydrochloric acid and potassium permanganate solution.

(d) Action of dilute hydrochloric acid on sodium sulphide.

(e) Action of hydrochloric acid on sodium bicarbonate.

Answer

(a) Na₂S₂O₃ + 2HCl ⟶ 2NaCl + S + H₂O + SO₂ ↑

(b) Ca(HCO₃)₂ + 2HCl ⟶ CaCl₂ + 2H₂O + 2CO₂ ↑

(c) 2KMnO₄ + 16HCl →ΔΔ​ 2KCl + 2MnCl₂ + 8H₂O + 5Cl₂↑

(d) Na₂S + 2HCl ⟶ 2NaCl + H₂S [g.] ↑

(e) NaHCO₃ + HCl ⟶ NaCl + H₂O + CO₂ ↑

Question 11

Give balanced equations with conditions, if any, for the following conversions

(a) Sodium Chloride ⟶ Hydrogen Chloride

(b) Hydrogen Chloride ⟶ Iron (II) chloride

(c) Hydrogen Chloride ⟶ Ammonium chloride

(d) Hydrogen Chloride ⟶ Lead chloride.

Answer

(a) NaCl+H2SO4→<200°CNaHSO4+HCl [g]NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g] ↑

(b) Fe + 2HCl (dil.) ⟶ FeCl₂ + H₂ [g]

(c) NH₄OH + HCl (dil.)⟶ NH₄Cl + H₂O

(d) PbO2+4HCl→ΔPbCl2+2H2O+Cl2PbO2​+4HClΔ​PbCl2​+2H2​O+Cl2​ ↑

Question 12

Explain why

(a) anhydrous HCl is a poor conductor while aqueous HCl is an excellent conductor.

(b) when the stopper of a bottle full of hydrogen chloride gas is opened there are fumes in the air.

(c) a solution of hydrogen chloride in water turns blue litmus red and conducts electricity, while a solution of the same gas in toluene

(i) has no effect on litmus, and

(ii) does not conduct electricity.

(d) thick white fumes are formed when a glass rod dipped in NH₄OH is brought near the mouth of a bottle full of HCl gas.

(e) dry hydrogen chloride gas does not affect a dry strip of blue litmus paper, but it turns red in the presence of a drop of water.

(f) hydrogen chloride gas is not collected over water.

(g) dilute hydrochloric acid cannot be concentrated by boiling beyond 22.2%.

(h) Hydrogen chloride gas cannot be dried over quick lime.

Answer

(a) Anhydrous HCl is a gas and does not contain any ions, hence it is a poor conductor of electricity. On the other hand, aqueous HCl (HCl dissolved in water) forms ions in solution, and thus becomes an excellent conductor of electricity.

HCl + H₂O ⟶ H₃O⁺ + Cl^-

(b) When hydrogen chloride gas is exposed to air, it gives white fumes, due to the formation of hydrochloric acid on dissolving in atmospheric water vapour.

(c) A solution of hydrogen chloride in water gives ions,

HCl + H₂O ⟶ H₃O⁺ + Cl^-

These ions are responsible for conducting electricity and turning blue litmus red, due to the presence of hydronium [H₃O⁺] ions which make aqueous solution of HCl acidic in nature.

Toluene is an organic solvent and HCl is a covalent compound. A solution of HCl in toluene contains only molecules and not ions due to which it does not conduct electricity. The absence of hydronium [H₃O⁺] ions make the solution neutral and it does not effect litmus paper.

(d) When a glass rod dipped in ammonium hydroxide (NH₄OH) is brought near the mouth of a bottle full of HCl gas, then it leads to the formation of dense white fumes due to the production of ammonium chloride.

NH₄OH + HCl ⟶ NH₄Cl + H₂O

(e) Dry hydrogen chloride gas does not contain any ions. Due to the absence of hydronium [H₃O⁺] ions, it is neutral and does not affect a dry strip of blue litmus paper. On the other hand, in the presence of a drop of water, HCl dissolves in it and dissociates into hydronium [H₃O⁺] ions and chloride ions [Cl^-]

HCl + H₂O ⟶ H₃O⁺ + Cl^-

The presence of hydronium [H₃O⁺] ions makes the aqueous solution acidic and blue litmus turns red.

(f) Hydrogen chloride gas is not collected over water since it is highly soluble in water.

(g) Hydrochloric acid forms a constant boiling mixture at 110°C, 22.2% by weight. On boiling further, the mixture evolves out the vapours of both acid and water in the same proportion as in the liquid.

Hence, dilute HCl cannot be concentrated beyond 22.2% by boiling.

(h) Quicklime [CaO] is alkaline in nature and it reacts with HCl forming the respective chloride. Hence, it can't be used as a drying agent.

Exercise 8 — Long Answer Type

Question 1

Draw a labelled diagram for the laboratory preparation of hydrogen chloride gas and answer the following.

(a) Name the acid used. Why is this particular acid preferred to other acids?

(b) Give the balanced equation for the reaction.

(c) Name the drying agent used in drying hydrogen chloride gas.

(d) Phosphorus pentoxide and calcium oxide are good drying agents, but they cannot be used to dry hydrogen chloride gas. Why?

(e) Why is direct absorption of HCl gas in water not feasible?

(f) What arrangement is done to dissolve HCl gas in water.

Answer

The labelled diagram for the laboratory preparation of hydrogen chloride gas is shown below:

(a) Conc. H₂SO₄ is used for the preparation of hydrogen chloride gas in the laboratory.

As conc. H₂SO₄ is non-volatile and has a high boiling point, therefore, it displaces the volatile hydrogen chloride from the salt sodium chloride. Hence, conc. H₂SO₄ is used as a reactant in the laboratory preparation of HCl from sodium chloride.

(b) NaCl+H2SO4→<200°CNaHSO4+HCl [g.]NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g.]

(c) Conc. H₂SO₄

Reason — Drying agent used for drying should only remove the moisture and not react with it, hence, conc. sulphuric acid is used as the drying agent.

(d) Phosphorus pentoxide and calcium oxide are good drying agents, but they cannot be used to dry hydrogen chloride gas since they react with it.

2P₂O₅ + 3HCl ⟶ POCl₃ + 3HPO₃

CaO + 2HCl ⟶ CaCl₂ + H₂O

(e) Direct absorption of hydrogen chloride gas in water is not feasible because it causes back suction in the delivery tube.

1. Hydrogen chloride gas is extremely soluble in water.

2. If a delivery tube through which HCl gas is passed is directly immersed in water, the rate of absorption of HCl gas is high and hence a partial vacuum is created in the tube.

3. The pressure outside being higher causes the water to be pushed up into the delivery tube and damages the apparatus. This is called back-suction.

(f) A special funnel arrangement is used to dissolve HCl gas in water as it provides a large surface area for absorption while preventing back-suction. The rim of the funnel is positioned so that it just touches the water in the trough. If back-suction occurs, the water rises up the funnel and the air gap between the rim of the funnel and the water's surface equalizes the pressure inside and outside.

Question 2

The given set up in the figure is for the preparation of an acid

(a) Name the acid prepared by this method.

(b) Name the reactants used.

(c) Why an empty flask is used?

(d) What is the drying agent used? Why is this drying agent chosen ?

(e) What is the role of inverted funnel in the arrangement?

Answer

(a) Hydrochloric acid (HCl)

(b) The reactants used are sodium chloride and sulphuric acid.

(c) The empty flask acts as an Anti-Suction device. If back suction takes place then the water gets collected in it and will not reach the generating flask.

(d) The drying agent used is Concentrated Sulphuric acid. It is chosen as drying agent because it does not react with HCl.

(e) The role of the inverted funnel in the arrangement is -

1. It prevents or minimizes back suction of water.

2. It provides a large surface area for absorption of HCl gas.

Question 3

How will you prove that Hydrochloric acid contains

(i) hydrogen

(ii) chlorine.

Write equations for the reactions.

Answer

(i) Using an active metal below magnesium

Fe + 2HCl ⟶ FeCl₂ + H₂↑

(ii) Using an oxidising agent not containing lead.

MnO₂ + 4HCl ⟶ MnCl₂ + 2H₂O + Cl₂↑

Question 4

Give three distinct tests [apart from using an indicator] you would carry out with solution of HCl to illustrate the typical properties of an acid.

Answer

(i) Action on metals — Hydrochloric acid reacts with metals above hydrogen in the activity series forming metallic chlorides and evolving hydrogen.

Ca + 2HCl ⟶ CaCl₂ + H₂ ↑

(ii) Action on oxides — Hydrochloric acid reacts with oxides to form salt and water only.

CuO + 2HCl ⟶ CuCl₂ + H₂O

(iii) With salts of weaker acids — Hydrochloric acid decomposes salts of weaker acids.

Na₂CO₃ + 2HCl ⟶ 2NaCl + H₂O + CO₂ ↑

Question 5

Convert:

(a) Two soluble metallic nitrates to insoluble metallic chlorides using dil. HCl.

(b) Insoluble iron(II) oxide to a soluble compound.

(c) Insoluble metal carbonate to a soluble chloride.

(d) Metal sulphide to an offensive smelling gas.

Answer

(a) Pb(NO₃)₂ + 2HCl ⟶ PbCl₂ + 2HNO₃Hg₂(NO₃)₂ + 2HCl ⟶ Hg₂Cl₂ + 2HNO₃

(b) FeO + 2HCl ⟶ FeCl₂ + H₂O

(c) CaCO₃ + 2HCl ⟶ CaCl₂ + H₂O + CO₂ ↑

(d) Na₂S + 2HCl ⟶ 2NaCl + H₂S ↑

Question 6

Study the flow chart and give balanced equations with conditions for the conversions A, B, C, D and E

Answer

The balanced chemical reactions are:

A : NaCl+H2SO4→<200°CNaHSO4+HCl [g]NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g] ↑

B : Zn+2HCl ( dil.)→ΔZnCl2+H2Zn+2HCl ( dil.)Δ​ZnCl2​+H2​ ↑

C : AgNO₃ + HCl ⟶ AgCl (white ppt.) + HNO₃

D : MnO2+4HClConc.→ΔMnCl2+2H2O+Cl2MnO2​+Conc.4HCl​Δ​MnCl2​+2H2​O+Cl2​ ↑

E : NaHCO₃ + HCl ⟶ NaCl + H₂O + CO₂ ↑

Question 7

In the laboratory preparation of hydrochloric acid, hydrogen chloride gas is dissolved in water.

(a) Draw a diagram to show the arrangement used for the absorption of HCl gas in water.

(b) State why such an arrangement is necessary. Give two reasons for the same.

(c) Write balanced chemical equations for the laboratory preparation of HCl gas when the reaction is :

    (A) below 200°C

    (B) above 200°C

Answer

(a) Below diagrams show the special funnel arrangement used for the absorption of HCl gas in water:

(b) The reasons are :

1. Prevents or minimizes back-suction of water.

2. Provides a large surface area for the absorption of the HCl gas.

(c) The equations are:

(A) NaCl+H2SO4→<200°CNaHSO4+HCl [g]NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g] ↑

(B) 2NaCl+H2SO4→>200°CNa2SO4+2HCl [g]2NaCl+H2​SO4​>200°C​Na2​SO4​+2HCl [g] ↑

Question 8

Study the figure given below and answer the questions that follow :

(i) Identify the gas Y.

(ii) What property of gas Y does this experiment demonstrate?

(iii) Name another gas which has the same property and can be demonstrated through this experiment.

Answer

(i) Dry HCl (Hydrogen chloride) gas is the gas Y

(ii) High solubility of HCl in water

(iii) Ammonia (NH₃) gas also demonstrates high solubility in water.

Question 9

Refer to the diagram given below and write balanced equations with conditions, if any, for the following conversions P to S.

Answer

P — NaCl+H2SO4→<200°CNaHSO4+HCl [g]NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g] ↑

Q — Fe + 2HCl (dil.) ⟶ FeCl₂ + H₂ [g]

R — NH₄OH + HCl (dil.)⟶ NH₄Cl + H₂O

S — PbO2+4HCl→ΔPbCl2+2H2O+Cl2PbO2​+4HClΔ​PbCl2​+2H2​O+Cl2​ ↑

Question 10

State your observations:

(a) HCl gas is passed through lead nitrate solution and the mixture is heated.

(b) Hydrochloric acid is added to silver nitrate solution.

(c) Ammonium hydroxide solution is added to the resultant product of part (b).

Answer

(a) When HCl gas is passed through lead nitrate, white precipitate of lead chloride is formed.

Pb(NO₃)₂ + 2HCl ⟶ PbCl₂ ↓ + 2HNO₃

(b) Hydrochloric acid, when reacted with silver nitrate solution it gives a thick curdy white precipitate of silver chloride. This white precipitate is insoluble in nitric acid.

AgNO₃ + HCl ⟶ AgCl ↓ + HNO₃

(c) On addition of ammonium hydroxide, the resultant of part (b) i.e., thick curdy white precipitate of silver chloride dissolves and forms a complex salt called diammine silver (I) chloride.

AgCl + 2NH₄OH ⟶ [Ag(NH₃)₂Cl)] + 2H₂O

Question 11

Distinguish by using HCl.

(a) Lead nitrate solution and silver nitrate solution.

(b) Potassium sulphite and potassium sulphide.

Answer

(a) On reaction with HCl, lead nitrate solution gives white precipitate which can be dissolved in hot water.

Pb(NO₃)₂ + 2HCl ⟶ PbCl₂ ↓ + 2HNO₃

Whereas, silver nitrate solution gives thick curdy white precipitate which is insoluble in hot water.

AgNO₃ + HCl ⟶ AgCl ↓ + HNO₃

(b) On reaction with HCl, potassium sulphite gives SO₂ gas with pungent odour

K₂SO₃ + 2HCl ⟶ 2KCl + H₂O + SO₂ ↑

However, potassium sulphide gives H₂S gas with rotten eggs odour.

K₂S + 2HCl ⟶ 2KCl + H₂S ↑

Question 12

The following questions pertain to the laboratory preparation of hydrogen chloride gas:

(a) Write the equation for it's preparation mentioning the conditions required.

(b) Name the drying agent used in the above preparation and give a reason for the choice.

(c) State a safety precaution taken during the preparation of hydrochloric acid.

Answer

(a) The equation for the laboratory preparation of hydrogen chloride gas :

NaCl+H2SO4→<200°CNaHSO4+HCl [g]NaCl+H2​SO4​<200°C​NaHSO4​+HCl [g] ↑

(b) Concentrated sulphuric acid is used as the drying agent used in the above preparation.

Reason — Drying agent used for drying should only remove the moisture and not react with it, hence, conc. sulphuric acid is used as the drying agent. Other drying agents like phosphorous pentoxide (P₂O₅) and quick lime (CaO) cannot be used since they react with hydrogen chloride gas.

(c) Temperature is maintained at nearly 200°C as at higher temperatures above 200°C the glass apparatus may crack, fuel is wasted, sodium sulphate formed, forms a hard crust which sticks to the glass and is difficult to remove.

Question 13

Identify the gas evolved and give the chemical test in each of the following cases.

Dilute hydrochloric acid reacts with:

(i) Iron [II] sulphide.

(ii) Sodium sulphite.

Answer

(i) H₂S gas is evolved when dilute hydrochloric acid reacts with Iron [II] sulphide.

FeS + 2HCl ⟶ FeCl₂ + H₂S ↑

(ii) SO₂ is evolved when dilute hydrochloric acid reacts with sodium sulphite.

Na₂SO₃ + 2HCl ⟶ 2NaCl + H₂O + SO₂ [g] ↑

chemical bonding

Overview of Chemical Bonding

Chemical bonding refers to the forces that hold atoms together in compounds. These bonds can be classified into several types, primarily ionic, covalent, and metallic bonds.

Types of Chemical Bonds

Ionic Bonds

• Formed between metals and nonmetals.

• Involves the transfer of electrons from one atom to another.

• Creates charged ions: cations (positive) and anions (negative).

• Characterized by strong electrostatic forces of attraction between oppositely charged ions.

Covalent Bonds

• Formed between two nonmetals.

• Involves the sharing of electron pairs between atoms.

• Can be single, double, or triple bonds depending on the number of shared electron pairs.

• Results in the formation of molecules.

Metallic Bonds

• Formed between metal atoms.

• Involves a 'sea of electrons' that are delocalized over a lattice of metal cations.

• Gives metals their characteristic properties such as conductivity and malleability.

Bonding Theories

Valence Shell Electron Pair Repulsion (VSEPR) Theory

• Predicts the geometry of molecules based on electron pair repulsion.

• Electron pairs arrange themselves to minimize repulsion, leading to specific shapes.

Molecular Orbital Theory

• Describes the formation of molecular orbitals from the combination of atomic orbitals.

• Electrons in molecules occupy molecular orbitals that can be bonding, antibonding, or non-bonding.

Properties of Compounds Based on Bonding

Properties of Ionic Compounds

• High melting and boiling points due to strong ionic bonds.

• Conduct electricity when dissolved in water or melted.

• Generally soluble in water but not in nonpolar solvents.

Properties of Covalent Compounds

• Lower melting and boiling points compared to ionic compounds.

• Do not conduct electricity in solid or liquid form.

• Solubility varies widely; some are soluble in water, while others are not.

Properties of Metallic Compounds

• Good conductors of heat and electricity.

• Malleable and ductile due to the flexibility of metallic bonds.

• Have a shiny appearance due to the ability to reflect light.

Conclusion

Chemical bonding is fundamental to understanding the structure and properties of matter. The type of bond influences the physical and chemical properties of substances, which is crucial for various applications in chemistry and materials science.

The Importance of Understanding the Reproductive System for Overall Health and Wellness

Progress Check 1

Question 1

Tick-mark the correct meaning of reproduction

(i) increase in population

(ii) increase in the number of parents

(iii) production of new individuals of the same kind

(iv) production of identical individuals

Answer

production of new individuals of the same kind

Question 2

State very briefly the chief function of each of the following :

(i) Seminal vesicles

(ii) Prostate gland

(iii) Cowper's gland

(iv) Sperm duct (vas deferens)

Answer

(i) Seminal vesicles produce a secretion that serves as a medium for the transportation of the sperms.

(ii) It pours an alkaline secretion into the semen as it passes through the urethra. It neutralises acid in female's vagina.

(iii) The secretion of Cowper's gland serves as a lubricant.

(iv) Sperm duct (vas deferens) help in the transportation of the sperms from the testes upwards to the abdomen.

Progress Check 2

Question 1

State whether the following statements are True (T) or False (F):

(i) One egg is released from each of the two ovaries every month.

(ii) The enlarged mature follicle bursts to release the egg.

(iii) The egg is passed down through the oviduct by muscular contractions.

(iv) Clitoris is equivalent to the male penis.

(v) The vagina is a muscular tube.

Answer

(i) FalseCorrected Statement — One egg is released from one of the two ovaries every month.

(ii) True

(iii) True

(iv) True

(v) True

Progress Check 3

Question 1

Name the three main regions of the human sperm, and briefly mention the function of each.

Answer

The three main regions of human sperm and their function are:

1. Head (Acrosome) — It secretes an enzyme (hyaluronidase) which facilitates entry of sperm into the egg by dissolving the wall of the ovum.

2. Middle Piece (Mitochondria) — It provides energy for the activity of the sperm to swim.

3. Tail (Axial filament) — Lashing movements of tail helps in propulsion.

Question 2

Name the following :

(i) Three accessory glands of human male reproductive system.

(ii) Two hormones secreted from placenta.

(iii) Two types of twins.

(iv) Two layers of the wall of uterus.

Answer

(i) Three accessory glands of human male reproductive system are:

1. Seminal vesicles

2. Prostate gland

3. Bulbo-urethral gland (or Cowper's gland)

(ii) Two hormones secreted from placenta are:

1. Oestrogens

2. Progesterone

(iii) Two types of twins are:

1. Fraternal Twins

2. Identical Twins

(iv) Two layers of the wall of uterus are:

1. Endometrium

2. Myometrium

Question 3

List the substances which the foetus receives from the mother through placenta.

Answer

The foetus receives following substances from the mother through placenta:

1. Oxygen

2. Glucose

3. Amino acids

4. Lipids, fatty acids and glycerol

5. Vitamins

6. Mineral ions such as Na, K, Ca, Cl, etc.

7. Certain drugs

8. Alcohol, nicotine

9. Antibodies

10. Viruses

Question 4

How are carbon dioxide and urea, excreted by the foetus, removed?

Answer

The placenta is formed of two sets of finger-like projections, the villi. One set is given out by uterine wall and the other set by allantois from the embryo. These two set of villi are interlocked. The impurities excreted by foetus are exchanged by their capillaries to the capillaries of uterine wall (mother).

Question 5

Write one sentence each using the following terms pertaining to reproduction in humans.

(i) Gestation

(ii) 280 days

(iii) Head first

(iv) Placenta

(v) After-birth

(vi) Tied and cut

Answer

(i) The gestation period refers to the full term of the embryo in the uterus.

(ii) In humans, the gestation period is 280 days.

(iii) During parturition, the baby is pushed out by powerful contraction, head first.

(iv) Placenta is the disc like structure attached to the uterine wall.

(v) After about 15 minutes of birth of baby, the placenta breaks from the uterus and is expelled out as "after-birth".

(vi) The umbilical cord is tied and cut after birth.

Question 6

Does the foetus inside the mother's uterus breathe? Yes/No

Answer

No

Reason — No, the foetus inside the mother's uterus does not breathe in the same way as a born baby or an adult. The exchange of gases between the mother's blood and the foetal blood takes place in the placenta, and the foetus obtains the necessary oxygen and eliminates carbon dioxide through this process. The actual breathing, as in inhaling and exhaling air into the lungs, only begins after birth when the baby takes its first breath.

Question 7

Mention if the following statements are True (T) or False (F):

(i) Placenta produces certain hormones.

(ii) Amniotic fluid serves to provide oxygen to the foetus.

(iii) Heart and blood vessels have been formed by the end of five weeks of pregnancy.

(iv) Mother's blood flows into the foetus through placenta.

Answer

(i) True

(ii) FalseCorrected Statement — Amniotic fluid serves to provide protection to the foetus.

(iii) True

(iv) FalseCorrected Statement — Mother's blood and the foetal blood do not directly mix in the placenta. Instead, the placenta acts as a barrier between the maternal and foetal circulations to allow for the exchange of oxygen, nutrients, and waste products without direct mixing of blood.

Question 8

Complete the following by filling in the blanks 1 to 5 with appropriate words:

The human female gonads are ovaries. A maturing egg in the ovary is present in a sac of cells called ...............(1). As the egg grows larger, the follicle enlarges and gets filled with a fluid and is now called the ............... (2) follicle. The process of releasing the egg from the ovary is called ............... (3). The ovum is picked up by the oviductal funnel and fertilization takes place in the ...............(4). In about a week the blastocyst gets fixed in the endometrium of the uterus and this process is called ...............(5).

Answer

The human female gonads are ovaries. A maturing egg in the ovary is present in a sac of cells called follicle(1). As the egg grows larger, the follicle enlarges and gets filled with a fluid and is now called the Graafian (2) follicle. The process of releasing the egg from the ovary is called ovulation (3). The ovum is picked up by the oviductal funnel and fertilization takes place in the fallopian tube (4). In about a week the blastocyst gets fixed in the endometrium of the uterus and this process is called implantation (5).

Multiple Choice Type

Question 1

The male accessory gland whose secretion neutralizes the acidity of the urethra and vagina is:

1. Seminal vesicle

2. Prostate gland

3. Seminiferous tubule

4. Bulbo-urethral gland

Answer

Prostate gland

Reason — The secretion of prostate gland is alkaline in nature and it neutralises the acidity of the urethra and vagina.

Question 2

The onset of menstruation in women is called ;

1. Parturition

2. Menopause

3. Ovulation

4. Menarche

Answer

Menarche

Reason — The term used for onset of menstruation in young female is called Menarche.

Question 3

In the human menstrual cycle, the ovulation occurs around :

1. 7 days

2. 21 days

3. 28 days

4. 14 days

Answer

14 days

Reason — Ovulation occurs during mid-menstrual cycle.

Question 4

Fertilization takes place in :

1. Fallopian tube

2. Uterus

3. Vas deferens

4. Vagina

Answer

Fallopian tube

Reason — Fertilization takes place in oviduct or Fallopian tube.

Question 5

The packing tissues between the coils of the seminiferous tubules are called as :

1. Leydig cells

2. Hymen

3. Graafian follicle

4. Clitoris

Answer

Leydig cells

Reason — The packing tissues between the coils of the seminiferous tubules are called as interstitial cells or Leydig cells.

Question 6

Which of the following cannot pass readily through the placenta to the foetus ?

1. Antibodies

2. Amino acids

3. Alcohol

4. Haemoglobin

Answer

Haemoglobin

Reason — There is exchange of substances between the capillaries of foetus and mother but their blood never mixes. Therefore, there is no exchange of Haemoglobin.

Question 7

The thin-walled sac of skin in which testis descends is :

1. Seminal vesicle

2. Vas deferens

3. Scrotal sac

4. Epididymis

Answer

Scrotal sac

Reason — Testis descends into scrotal sac.

Question 8

The outermost layer of uterine wall around the foetus is :

1. Choroid

2. Allantois

3. Chorion

4. Amnion

Answer

Chorion

Reason — The outermost layer of uterine wall around the foetus is chorion.

Question 9

The period of pregnancy is called :

1. Parturition

2. Implantation

3. Copulation

4. Gestation

Answer

Gestation

Reason — The duration between fertilization and birth of baby is called gestation period. It is 280 days in case of humans.

Question 10

The canal through which each testis descends into the scrotum just before the birth of a male baby is :

1. Acrosome

2. Epididymis

3. Efferent duct

4. Inguinal canal

Answer

Inguinal canal

Reason — The canal through which each testis descends into the scrotum just before the birth of a male baby is inguinal canal.

Very Short Answer Type

Question 1

Name these:

(a) 3 male accessory glands in humans.

(b) 2 hormones secreted from the corpus luteum.

(c) 4 phases of the menstrual cycle.

(d) 2 types of twins.

(e) 3 membranous, protective layers around the foetus.

Answer

(a) 3 male accessory glands in humans are:

1. Seminal vesicle

2. Prostate gland

3. Cowper's gland

(b) 2 hormones secreted from the corpus luteum are:

1. Oestrogen

2. Progesterone

(c) 4 phases of the menstrual cycle are:

1. Menstrual phase

2. Follicular phase

3. Ovulatory phase

4. Luteal phase

(d) 2 types of twins are:

1. Fraternal Twins

2. Identical Twins

(e) 3 membranous, protective layers around the foetus are:

1. Chorion

2. Amnion

3. Allantois

Question 2

Rewrite the terms in the correct order so as to be in a logical sequence.

(a) Implantation, ovulation, child birth, gestation, fertilisation.

(b) Sperm duct, coitus, sperm, vagina, urethra.

(c) Sperm duct, penis, testes, sperms, semen.

(d) Puberty, menopause, menstruals, menarche, reproductive age.

(e) Graafian follicle, ostium, uterus, fallopian tube, ovum.

Answer

(a) Ovulation → fertilization → implantation → gestation → child birth

(b) Sperm → sperm duct → urethra → coitus → vagina

(c) Testes → Sperms → Sperm duct → Semen → Penis

(d) Reproductive age → Puberty → Menarche → Menstruals → Menopause

(e) Ovum → Graafian follicle → Ostium → Fallopian tube → Uterus.

Question 3

Give appropriate terms for the following processes:

(a) The onset of reproductive phase in a female.

(b) Rupture of follicle and release of ovum from the ovary.

(c) Monthly discharge of blood and disintegrated tissues in human female.

(d) Process of fusion of ovum and sperm.

(e) Fixing of developing zygote (blastocyst) on the uterine wall.

Answer

(a) Menarche

(b) Ovulation

(c) Menstruation

(d) Fertilization

(e) Implantation

Question 4

Match the items in column I with those in column II and write down the matching pairs (some may not match)

Column I	Column II
(a) Acrosome	(i) An embryo which looks like human baby
(b) Gestation	(ii) Luteinizing hormone
(c) Menopause	(iii) Ovum producing cells
(d) Foetus	(iv) Semen
(e) Oogenesis	(v) Spermatozoa
(f) Ovulation	(vi) Complete stoppage of menstrual cycle
	(vii) Time taken by a fertilized egg till the delivery of baby

Answer

Column I	Column II
(a) Acrosome	(v) Spermatozoa
(b) Gestation	(vii) Time taken by a fertilized egg till the delivery of baby
(c) Menopause	(vi) complete stoppage of menstrual cycle
(d) Foetus	(i) An embryo which looks like human baby
(e) Oogenesis	(iii) ovum producing cells
(f) Ovulation	(ii) Luteinizing hormone

Question 5

Given below are some groups of terms. In each group, one pair indicates the relationship between the two terms. Rewrite and complete the second pair on a similar basis.

(a) Sperm : Spermatogenesis : Ovum : ...............

(b) Female gonad : Ovaries :: Male gonad : ...............

(c) Follicle cells : Ova :: ............... : Sperms

(d) Leydig cells : Testosterone :: ............... : Oestrogen

(e) Follicular phase : 5-12 days :: Luteal phase : ............... days.

Answer

(a) Sperm : Spermatogenesis : Ovum : Oogenesis

(b) Female gonad : Ovaries :: Male gonad : testes

(c) Follicle cells : Ova :: Seminiferous tubules : Sperms

(d) Leydig cells : Testosterone :: Corpus Luteum : Oestrogen

(e) Follicular phase : 5-12 days :: Luteal phase : 15-28 days.

Question 6

Choose the odd one out from the group of terms given below and write the category for the remaining terms:

(a) Testis, Epididymis, Uterine tube, Sperm duct.

(b) Seminal vesicle, Seminiferous tubule, Prostate gland, Cowper’s gland.

(c) Uterus, Ureter, Oviduct, Ovaries.

(d) Choroid, Chorion, Amnion, Allantois.

(e) Zona pellucida, Acrosome, Axial filament, Middle piece.

Answer

(a) Odd term: Uterine tubeCategory: Male reproductive system organs

(b) Odd term: Seminiferous tubuleCategory: Male accessory glands

(c) Odd term: UreterCategory: Female reproductive system organs

(d) Odd term: ChoroidCategory: Protective membranes around foetus.

(e) Odd term: Zona pellucidaCategory: Parts of sperm

Short Answer Type

Question 1

(a) State whether the following statements are TRUE (T) or FALSE (F).

1. Fertilisation occurs in vagina.

2. Uterus is also known as birth canal.

3. Nutrition and oxygen diffuse from the mother's blood into the foetus's blood through amnion.

(b) Rewrite any two of the wrong statements by correcting only one word either at the beginning or at the end of the sentence.

Answer

(a)

1. False

2. False

3. False

(b)

1. Corrected Sentence — Fertilization occurs in the fallopian tube.

2. Corrected Sentence — Vagina is also known as the birth canal.

3. Corrected Sentence — Nutrition and oxygen diffuse from the mother's blood into the foetus's blood through placenta.

Question 2

Complete the following table by writing the name of the structure or the function of the given structure:

Structure	Function
(1) Corpus luteum	1. ...............
(2)...............	2. Produces male gametes in mass
(3)Leydig cells	3. ...............
(4)...............	4. Stores the sperms until they mature and become mobile
(5)Umbilical cord	5. ...............
(6)Fallopian tube	6. ...............

Answer

Structure	Function
(1) Corpus luteum	1. Secretes progesterone & other hormones to prepare the uterine wall for the receival of the embryo.
(2) Testes	2. Produces male gametes in mass
(3) Leydig cells	3. Produce the male hormone testosterone
(4) Epididymis	4. Stores the sperms until they mature and become mobile
(5) Umbilical cord	5. Connects placenta with foetus
(6) Fallopian tube	6. The site of fertilization for the sperm and ovum.

Question 3

Given below are the names of certain stages/substances related to reproduction and found in human body. Answer the questions related to them.

(a) Foetus

• Where is it contained?

• How does it differ from embryo?

(b) Hyaluronidase

• Is it an enzyme or simply a protein?

• What is its function?

(c) Morula

• What is this stage?

• Name the stage which comes next to it.

(d) Amniotic fluid

• Where is it found?

• What are its functions?

(e) Placenta

• What are the two sources that form placenta?

• Name any two main substances which pass from foetus to mother through placenta.

• Name any two hormones it produces.

(f) Implantation

• The development stage that undergoes this process.

• The approximate time after fertilisation, when it occurs.

Answer

(a) Foetus —

• It is contained in the uterus.

• In foetus, limbs have appeared and resembles the humans unlike the embryo which is a growing or dividing zygote.

(b) Hyaluronidase —

• Enzyme

• It is an enzyme secreted by the sperm that allows the sperm to penetrate the egg.

(c) Morula —

• It is the stage in the development of human embryo which consists of a spherical mass of cells.

• Blastocyst

(d) Amniotic fluid —

• Between amnion and embryo

• The functions of Amniotic fluid are:

  1. It protects the embryo from physical damage by jerks or mechanical shocks.

  2. Keeps an even pressure all around the embryo.

  3. Allows the foetus some restricted movement.

  4. Prevents sticking of the foetus to the amnion.

(e) Placenta —

• Placenta is formed by two sets of minute finger like processes called the villi. One set of villi is from the uterine wall and the other set is from the allantois.

• Carbon dioxide and Urea pass from foetus to mother through placenta.

• Two hormones produced by Placenta are Progesterone and Oestrogens.

(f) Implantation —

• Blastocyst

• It occurs in about 5-7 days after fertilisation.

Question 4

Write important functions of the following :

(a) Inguinal canal

(b) Testis

(c) Ovary

(d) Oviduct

(e) Uterus

Answer

(a) Inguinal canal allows the descent of testes into scrotal sac.

(b) Testis produce and store sperms and also secrete testosterone hormone.

(c) Ovaries produce the egg cells, called the ova. The corpus luteum in the ovary secretes two hormones — Oestrogen and Progesterone.

(d) Oviducts (Fallopian tubes) carry the released ovum from the ovary to the uterus. Fertilisation also occurs in the Oviduct.

(e) The uterus is responsible for nurturing and housing a developing fetus during pregnancy.

Question 5

Write the specific location of each of the following :

(a) Seminal vesicle

(b) Uterus

(c) Placenta

(d) Acrosome

(e) Vagina

Answer

(a) Seminal vesicles are located between the posterior surface of the urinary bladder and the rectum in males.

(b) Uterus is situated in the pelvic cavity between the urinary bladder and the rectum in females.

(c) Placenta is attached to the uterine wall.

(d) Head of sperm.

(e) Vagina starts from lower end of uterus to outside.

Descriptive Type

Question 1

Define the following terms:

(a) Reproduction

(b) Hernia

(c) Ovulation

(d) Puberty

(e) Fertilization

(f) Hymen

Answer

(a) Reproduction — Reproduction is the process of formation of new individuals by sexual or asexual means, which can repeat the process in their own turn.

(b) Hernia — Hernia is an abnormal condition which is caused when the intestine due to the pressure in abdomen bulges into the scrotum through the inguinal canal.

(c) Ovulation — Ovulation is the rupture of the follicle releasing the egg .

(d) Puberty — Puberty is the period during which immature reproductive system in boys and girls matures and becomes capable of reproduction.

(e) Fertilization — The fusion of the male gamete (sperm) and the female gamete (ovum) to form a zygote is called fertilisation.

(f) Hymen — Hymen is a thin membrane which partially covers the opening of the vagina in young females.

Question 2

Distinguish between the following pairs:

(a) Spermatogenesis and oogenesis

(b) Implantation and gestation

(c) Pregnancy and parturition

(d) Placenta and umbilical cord

(e) Identical and fraternal twins

(f) Menarche and menopause

Answer

(a) Difference between spermatogenesis and oogenesis —

Spermatogenesis	Oogenesis
It is the process of production of sperms in seminiferous tubules of testes.	Oogenesis is the process in which the ova - producing cells give rise to the mature ovum.

(b) Difference between implantation and gestation —

Implantation	Gestation
The process of fixing of the blastocyst to the wall of the uterus/endometrium is termed implantation.	The full term of the development of the embryo in the uterus is called gestation.

(c) Difference between pregnancy and parturition —

Pregnancy	Parturition
It is the state of carrying a developing embryo or a foetus within the female body.	It is the act of expelling the full term foetus from the mother's uterus at the end of gestation.

(d) Difference between placenta and umbilical cord —

Placenta	Umbilical cord
Placenta is the intimate connection established between the foetal membranes and uterine wall permitting diffusion of nourishment from the mother's blood to that of the growing foetus and disposal of wastes from the blood of the foetus to that of the mother.	It is a cord containing blood vessels which connects the placenta with the foetus.

(e) Difference between identical and fraternal twins —

Identical twins	Fraternal twins
Identical twins are produced by a single fertilised egg getting split into two parts during its early stages of cell division.	Fraternal twins are produced by two different eggs which are released from the ovaries at a time and both got fertilised together.
Identical twins are either both boys or both girls.	Fraternal twins may be either both boys or both girls or one boy and one girl.

(f) Difference between Menarche and Menopause —

Menarche	Menopause
It is the onset of menstruation in a young female at about the age of 13 years.	It is the permanent stoppage of menstruation in females at about the age of 45 years.

Question 3

What is the significance of the testes being located in the scrotal sacs outside the abdomen? Can there be any abnormal situation regarding their location? If so, what is that and what is the harm caused due to it?

Answer

Testes are responsible for the production of male gametes i.e. sperms. The normal body temperature does not allow the maturation of the sperms. Being suspended outside the body cavity, the temperature in the scrotal sac is 2 to 3°C lower than that of the body which is the suitable temperature for the maturation of the sperms.When it is too hot, the skin of the scrotum loosens so that the testes hang down away from the body. When it is too cold, the skin contracts in a folded manner and draws the testes closer to the body for warmth.In an abnormal condition, in the embryonic stage, the testes do not descend into the scrotum. It can lead to sterility or incapability to produce sperms.

Question 4

What are the secondary sexual characteristics in the human male and female respectively?

Answer

Secondary sexual characteristics in males:

1. Deeper voice

2. Hair growth on the face in the form of beard and moustache

3. Stronger muscular built

Secondary sexual characteristics in females:

1. High pitched voice

2. Broad hips

3. Development of breasts

Question 5

What are the accessory reproductive organs?

Answer

The accessory reproductive organs include all those structures, ducts and glands which help in the transfer and meeting of two kinds of sex cells leading to fertilization and in the growth and development of the egg up to the birth of the baby.

For example: Uterus in females, Penis in males.

Question 6

Differentiate between the primary and accessory reproductive organs.

Answer

Primary Reproductive Organs	Accessory Reproductive Organs
The primary reproductive organs do not help in the development of baby.	The accessory organs help in the growth and development of egg up to the birth of baby.
The primary reproductive organs produce sex cells — the sperms and eggs.	The accessory reproductive organs help in the transfer and meeting of two kinds of sex cells leading to fertilization.
Example: Testes in males and Ovaries in females.	Example: Penis in males, Uterus, Vagina in female.

Question 7

Name and describe very briefly, the stages in the development of human embryo.

Answer

The different stages in the development of human embryo are described below:

Question 8

Is it correct to say that the testes produce testosterone? Discuss.

Answer

Testosterone is the male reproductive hormone produced by the interstitial cells or the Leydig cells. These cells are located in the testes. They serve as a packing tissue between the coils of the seminiferous tubules. Therefore, it can be said that the testes produce the male hormone testosterone.

Structured / Application / Skill Type

Question 1

Given below is a diagram of two systems together in the human body.

(a) Name the systems.

(b) Name the parts numbered 1-10.

(c) Describe the functions of the parts 3, 4, 5 and 6.

(d) What will happen if the part 3 on both sides gets blocked?

Answer

(a) Excretory system and Female Reproductive system.

(b) The parts numbered 1-10 are:

• 1 → Kidney

• 2 → Ureter

• 3 → Fallopian Tube

• 4 → Oviducal Funnel

• 5 → Ovary

• 6 → Uterus

• 7 → Urinary Bladder

• 8 → Cervix

• 9 → Vagina

• 10 → Vulva

(c) Functions of the parts are:

• Fallopian Tube (part 3) — The fallopian tubes carry the ovum released from the ovary to the uterus.

• Oviducal Funnel (part 4) — It is the funnel shaped distal end of the ovary which picks up the released ovum and pushes it further on its passage into the fallopian tube.

• Ovary (part 5) — Ovary produces female gametes i.e. ova.

• Uterus (part 6) — Uterus allows the growth and development of the embryo.

(d) If fallopian tube (part 3) on both sides gets blocked, the ovum released by the ovary will not be pushed into the oviduct and hence, there will be no possibility of fertilisation.

Question 2

The figure given ahead is an organ system of humans. Study the same and answer the following questions.

(a) Identify the organ system.

(b) Label the guidelines 1 to 7.

(c) Write one important role of parts 3 and 6.

(d) Name the cells of part 1 that produce testosterone.

(e) What is the significance of the part 1 being located in a separate sac suspended outside the body ?

Answer

(a) Male Reproductive Organ System

(b)

• 1 → Testes

• 2 → Scrotal sac

• 3 → Epididymis

• 4 → Sperm duct

• 5 → Seminal vesicle

• 6 → Bulbo-Urethral Gland

• 7 → Urethra

(c) Part 3 (Epididymis) — It stores the sperms for some days during which they mature and become motile.Part 6 (Bulbo-Urethral Gland) — Their secretion serves as a lubricant.

(d) Leydig cells

(e) The normal body temperature does not allow the maturation of the sperms. Being suspended outside the body cavity, the temperature in the scrotal sac is 2 to 3°C lower than that of the body which is the suitable temperature for the maturation of the sperms.

Question 3

The figure given below is an important gonad of humans. Study the figure and answer the following questions.

(a) Identify the organ. Write its specific location in the body.

(b) Label the parts shown in the figure as 1 to 4.

(c) Write important functions of parts 2 and 4.

(d) Name one cellular structure and one hormone which are produced in part 3.

(e) Draw a neat and labelled diagram of the cellular structure mentioned by you in (d).

Answer

(a) Testis.They are located in scrotal sac.

(b)

• 1 → Epididymis

• 2 → Efferent ducts

• 3 → Seminiferous tubules

• 4 → Sperm duct

(c) Efferent ducts (Part 2) conduct sperm to epididymis.Sperm duct (Part 4) transmit sperms from testes to urethra.

(d) Sperms and testosterone.

(e) Labelled diagram of the cellular structure of the sperm is given below:

Question 4

Given below is the outline of the male reproductive system. Name the parts labelled 1 to 8. Also name the corresponding structure of part (4) in the female reproductive system.

Answer

• 1 → Urinary bladder

• 2 → Ureter

• 3 → Bulbo-urethral glands

• 4 → Sperm duct/Vas deferens

• 5 → Urethra

• 6 → Testis

• 7 → Scrotum

• 8 → Epididymis

Fallopian tubes (oviducts) in females are analogous to sperm ducts in males. Sperm ducts carry sperms to the urethra, while fallopian tubes carry ova to the uterus.

Question 5

The diagram below is that of a developing human foetus in the womb. Study the same and answer the questions that follow:

(a) Name the parts '1' to '5' indicated by guidelines.

(b) What term is given to the period of development of the foetus in the womb?

(c) How many days does the foetus take to be fully developed?

(d) Mention two functions of the parts labelled '2' other than its endocrine functions.

(e) Name any one hormone produced by the part labelled '2'.

Answer

(a) The parts 1 to 5 are:

• 1 → Umbilical cord

• 2 → Placenta

• 3 → Amnion

• 4 → Mouth of uterus

• 5 → Muscular wall of uterus

(b) Gestation

(c) 280 days

(d) Placenta provides the foetus with oxygen and nutrients. In addition, the placenta also removes carbon dioxide and waste products of the foetus.

(e) Progesterone

Question 6

The figure given below is the human female reproductive system. Study the same and answer the following questions.

(a) Label the guidelines 1 to 6 shown in the figure.

(b) What is the normal gestation period in human ?

(c) Where are the sperms released during coitus ?

(d) Write two important functions of part 2.

(e) Mention the technical term for the fixing of developing zygote to the uterine wall.

Answer

(a) The labelled guidelines are:

• 1 → Vagina

• 2 → Ovary

• 3 → Funnel of Oviduct

• 4 → Fallopian tube

• 5 → Uterus

• 6 → Uterus lining

(b) 280 days

(c) Vagina

(d) Ovary releases egg and produces hormones (oestrogen, progesterone)

(e) Implantation

Question 7

The diagram below represents two reproductive cells A and B. Study the same and then answer the questions that follow:

(a) Identify the reproductive cells A and B

(b) Name the specific part of the reproductive system where the above cells are produced.

(c) Where in the female reproductive system do these cells unite?

(d) Name the main hormone secreted by the (1) ovary (2) testes.

(e) Name an accessory gland found in the male reproductive system and state the function of its secretion.

Answer

(a) The reproductive cells A and B are:

• A → Ovum

• B → Sperm

(b) Parts of the reproductive system where the above cells are produced are:

• Sperms are produced in the testis.

• The ovum is produced in the ovary.

(c) The reproductive cells unite in the fallopian tubes of the female reproductive system.

(d) The main hormone secreted are:

• Ovary → Oestrogen and progesterone

• Testis →Testosterone

(e) Accessory glands found in the male reproductive system along with their functions are mentioned below:

• Seminal vesicle — They produce a secretion which serves as a medium for the transportation of the sperms.

• Prostate gland — It produces an alkaline secretion which mixes with the semen and helps neutralise acid in female's vagina.

• Bulbo-urethral gland — They produce a secretion which serves as a lubricant.