e boook of science

1. Aluminium is used for making cooking uten¬sils. Which of the following properties of alu¬minium are responsible for the same?
(i) Good thermal conductivity
(ii) Good electrical conductivity
(iii) Ductility
(iv) High melting point
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (i) and (iv)

Answer

Answer: d

2. The most abundant metal in the earth’s crust is
(a) Iron
(b) Aluminium
(c) Calcium
(d) Sodium

Answer

Answer: b

3. The poorest conductor of heat among metals is
(a) Lead
(b) Mercury
(c) Calcium
(d) Sodium

Answer

Answer: a

4. Which property of metals is used for making bells and strings of musical instruments like Sitar and Violin?
(a) Sonorousness
(b) Malleability
(c) Ductility
(d) Conductivity

Answer

Answer: a

5. Al2O3 + 2NaOH → …… + H2O
(a) Al(OH)3
(b) Na2O
(c) NaAlO2
(d) AlNaO2

Answer

Answer: c

6. Which of the following is the correct arrange-ment of the given metals in ascending order of their reactivity?
Zinc, Iron, Magnesium, Sodium
(a) Zinc > Iron > Magnesium > Sodium
(b) Sodium > Magnesium > Iron > Zinc
(c) Sodium > Zinc > Magnesium > Iron
(d) Sodium > Magnesium > Zinc > Iron

Answer

Answer: d

7. Which of the following pairs will give dis-placement reactions?
(a) FeSO4 solution and Copper metal
(b) AgNO3 solution and Copper metal
(c) CuSO4 solution and Silver metal
(d) NaCl solution and Copper metal

Answer

Answer: b

8. Non-metals form covalent chlorides because
(a) they can give electrons to chlorine
(b) they can share electrons with chlorine
(c) they can give electrons to chlorine atoms to form chloride ions
(d) they cannot share electrons with chlorine atoms

Answer

Answer: b

9. Which of the following oxide(s) of iron would be obtained on prolonged reaction of iron with steam?
(a) FeO
(b) Fe2O3
(c) Fe3O4
(d) Fe2O3 and Fe2O4

Answer/ Explanation

Answer: c
Explaination: Reason: 3Fe (s) + 4H2O (g) → Fe3O4 (s) + 4H2 (g)

10. Which of tire following are not ionic compounds?
(i) KCl
(ii) HCl
(iii) CCl4
(iv) NaCl
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iii)

Answer

Answer: b

11. The electronic configuration of three elements X, Y and Z are as follows:
X = 2, 4, Y = 2, 7, Z = 2,1 Which two elements will combine to form an ionic compound and write the correct formula,
(a) X2Y
(b) YZ
(c) XZ3</sub
(d) Y2Z

Answer

Answer: b

12. The highly reactive metals like Sodium, Potas-sium, Magnesium, etc. are extracted by the
(a) electrolysis of their molten chloride
(b) electrolysis of their molten oxides
(c) reduction by aluminium
(d) reduction by carbon

Answer

Answer: a

13. Which of the following non-metal is lustrous?
(a) Sulphur
(b) Oxygen
(c) Nitrogen
(d) Iodine

Answer

Answer: d

14. Example of an amphoteric oxide is:
(a) Na2O
(b) K2O
(C) Al2O3
(d) MgO

Answer

Answer: c

15. Which one among the following is an acidic oxide?
(a) Na2O
(b) CO
(c) CO2
(d) Al2O3

Answer

Answer: c

16. The atomic number of an element ‘X’ is 12. Which inert gas is nearest to X?
(a) He
(b) Ar
(c) Ne
(d) Kr

Answer/ Explanation

Answer: c
Explaination: Reason: ‘X’ is Magnesium and Argon (Ar) with atomic number 12 is the closest inert gas to it.

17, The process in which a carbonate ore is heated strongly in the absence of air to convert it into metal oxide is called
(a) Roasting
(b) Reduction
(c) Calcination
(d) Smelting

Answer

Answer: c

18. Oxides of moderately reactive metals like Zinc, Iron, Nickel, Tin, Copper etc. are reduced by using
(a) Aluminium as reducing agent
(b) Sodium as reducing agent
(c) Carbon as reducing agent
(d) Calcium as reducing agent

Answer

Answer: c

19. In thermite welding a mixture of …… and …… is ignited with a burning magnesium ribbon which produces molten iron metal as large amount of heat is evolved.
(a) iron (III) oxide and aluminium powder
(b) iron (II) oxide and aluminium powder
(c) iron (III) chloride and aluminium powder
(d) iron (III) sulphate and aluminium powder

Answer

Answer: a

20. Galvanisation is a method of protecting iron from rudftng by coating with a thin layer of
(a) Galium
(b) Aluminium
(c) Zinc
(d) Silver

Answer

Answer: c

21. An element X is soft and can be cut with a knife. This is very reactive to air and cannot be kept open in air. It reacts vigorously with water. Identify the element from the following
(a) Mg
(b) Na
(c) P
(d) Ca

Answer

Answer: b

22. Reaction between X and Y forms compound Z. X loses electron and Y gains electron. Which of the following properties is not shown by Z?
(a) Has high melting point
(b) Has low melting point
(c) Conducts electricity in molten state
(d) Occurs as solid

Answer/ Explanation

Answer: c
Explaination: Reason: Z is an ionic compound. It has a high melting point.

1. What happens when a solution of an acid is mixed with a solution of a base in a test tube?
(i) Temperature of the solution decreases
(ii) Temperature of the solution increases
(in) Temperature of the solution remains the same
(iv) Salt formation takes place
(a) (i) and (iv)
(b) (i) and (iii)
(c) (ii) only
(d) (ii) and (iv)

Answer

Answer: d

2. When hydrogen chloride gas is prepared on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to
(a) absorb the evolved gas
(b) moisten the gas
(c) absorb moisture from the gas
(d) absorb Cl– ions from the evolved gas

Answer/ Explanation

Answer: c
Explaination: Reason: Guard tube drys (absorbs water) from calcium chloride on a humid day.

3. Which one of the following salts does not con-tain water of crystallisation?
(a) Blue vitriol
(b) Baking soda
(c) Washing soda
(d) Gypsum

Answer

Answer: b

4. In terms of acidic strength, which one of the following is in the correct increasing order?
(a) Water < Acetic acid < Hydrochloric acid
(b) Water < Hydrochloric acid < Acetic acid
(c) Acetic acid < Water < Hydrochloric acid
(d) Hydrochloric acid < Water < Acetic acid

Answer

Answer: a

5. What is formed when zinc reacts with sodium hydroxide?
(a) Zinc hydroxide and sodium
(b) Sodium zincate and hydrogen gas
(c) Sodium zinc-oxide and hydrogen gas
(d) Sodium zincate and water

Answer/ Explanation

Answer: b
Explaination: Reason: Zn + 2NaOH → Ma2Zn02 (Sodium Zincate) + H2

6. Tomato is a natural source of which acid?
(a) Acetic acid
(b) Citric acid
(c) Tartaric acid
(d) Oxalic acid

Answer

Answer: d

7. Brine is an
(a) aqueous solution of sodium hydroxide
(b) aqueous solution of sodium carbonate
(c) aqueous solution of sodium chloride
(d) aqueous solution of sodium bicarbonate

Answer

Answer: c

8. Na2CO3 . 10H2O is
(a) washing soda
(b) baking soda
(c) bleaching powder
(d) tartaric acid

Answer

Answer: a

9. At what temperature is gypsum heated to form Plaster of Paris?
(a) 90°C
(b) 100°C
(c) 110°C
(d) 120°C

Answer

Answer: b

10. How many water molecules does hydrated cal-cium sulphate contain?
(a) 5
(b) 10
(c) 7
(d) 2

Answer/ Explanation

Answer: d
Explaination: Reason: Chemical formula of hydrated calcium sulphate or gypsum is CaSO4.2H2O

11. Sodium carbonate is a basic salt because it is a salt of a
(a) strong acid and strong base
(b) weak acid and weak base
(c) strong acid and weak base
(d) weak acid and strong base

Answer

Answer: d

12. Alkalis are
(a) acids, which are soluble in water
(b) acids, which are insoluble in water
(c) bases, which are insoluble in water
(d) bases, which are soluble in water

Answer

Answer: d

13. Which of the following statements is correct about an aqueous solution of an acid and of a base?
(i) Higher the pH, stronger the acid
(ii) Higher the pH, weaker the acid
(in) Lower the pH, stronger the base
(iv) Lower the pH, weaker the base
(a) (i) and (iii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)

Answer/ Explanation

Answer: d
Explaination: Reason: Stronger the acid, lesser is the pH. Stronger the base, higher is the pH.