ICSE Class 10

General instructions: Answer all questions. Marks are shown in brackets [ ].

Objective

1. 1.
   Four grams of caustic soda contains

   1. a. 6.02 × 10²³ atoms of it
   2. b. 4 g atom of sodium
   [1]
2. 2.
   The vapour density of carbon dioxide [C = 12, O = 16]

   1. a. 32
   2. b. 16
   3. c. 44
   4. d. 22
   [1]
3. 3.
   What is the definition of atomic weight?

   1. A. The mass of one atom of an element on the scale where the C-12 isotope of carbon weighs 12.000 units.
   2. B. The total number of protons and neutrons in an atom of an element.
   3. C. The average mass of all naturally occurring isotopes of an element relative to hydrogen.
   4. D. The mass of one mole of atoms of an element expressed in grams.
   [1]
4. 4.
   (ii) The vapour density of a gas is 8. What would be the volume occupied by 24.0 g of the gas at STP?

   1. A. 11.2 dm³
   2. B. 22.4 dm³
   3. C. 33.6 dm³
   4. D. 44.8 dm³
   [1]
5. 5.
   How many moles of NaOH are present in 160 g of it?

   1. A. 2 moles
   2. B. 4 moles
   3. C. 8 moles
   4. D. 40 moles
   [1]
6. 6.
   Choose the correct answer from the options given below: The vapour density of carbon dioxide [C = 12, O = 16] (a) 32 (b) 16 (c) 44 (d) 22

   1. a. 32
   2. b. 16
   3. c. 44
   4. d. 22
   [1]
7. 7.
   The mass of 5.6 dm³ of a certain gas at STP is 12.0 g. What is the relative molecular mass of the gas?

   1. A. 24 a.m.u.
   2. B. 36 a.m.u.
   3. C. 48 a.m.u.
   4. D. 60 a.m.u.
   [1]
8. 8.
   The given sample of hydrochloric acid contains only 20% by weight of HCl, the rest being water. What mass of the acid will be required for reacting completely with 20 g of magnesium oxide?

   1. A. 36.5 g
   2. B. 91.25 g
   3. C. 182.5 g
   4. D. 365 g
   [1]
9. 9.
   44. Given that the relative molecular mass of copper oxide is 80, what volume of ammonia (measured at STP) is required to completely reduce 120 g of copper oxide? The equation for the reaction is: 3CuO + 2NH₃ → 3Cu + 3H₂O + N₂

   1. A. 11.2 litres
   2. B. 22.4 litres
   3. C. 33.6 litres
   4. D. 44.8 litres
   [1]
10. 10.
    Which of the following would occupy 22.4 litres at S.T.P.? 1. 32 g of oxygen gas 2. 2 moles of hydrogen gas 3. 6.022 × 10²³ molecules of ammonia (Atomic weights: O = 16, H = 1, N = 14)

    1. a. 1 and 2
    2. b. 1 and 3
    3. c. 2 and 3
    4. d. 1, 2 and 3
    [1]
11. 11.
    The reaction between aluminium carbide and water takes place according to the following equation: $$\mathrm{Al_4C_3} + 12\mathrm{H_2O} \rightarrow 3\mathrm{CH_4} + 4\mathrm{Al(OH)_3}$$. What volume of methane, measured at STP, is released from 14.4 g of aluminium carbide by excess of water?

    1. A. 2.24 L
    2. B. 6.72 L
    3. C. 13.44 L
    4. D. 22.4 L
    [1]
12. 12.
    Calculate the mass of iron in 10 kg of iron ore which contains 80% of pure ferric oxide.

    1. A. 5.6 kg
    2. B. 6.4 kg
    3. C. 4.8 kg
    4. D. 8.0 kg
    [1]
13. 13.
    What volume does one mole of chlorine gas occupy at standard temperature and pressure (S.T.P.)?

    1. A. 11.2 dm³
    2. B. 22.4 dm³
    3. C. 44.8 dm³
    4. D. 5.6 dm³
    [1]
14. 14.
    (i) What is the percentage of phosphorus in the fertilizer super-phosphate Ca(H₂PO₄)₂?

    1. A. 12.2%
    2. B. 26.5%
    3. C. 31.0%
    4. D. 45.8%
    [1]
15. 15.
    A compound has the following percentage composition: N = 21.21%, H = 6.06%, S = 24.24%, O = 48.48%. What is its empirical formula? (Atomic weights: H = 1, N = 14, S = 32, O = 16)

    1. A. NH₄SO₄
    2. B. (NH₄)₂SO₄
    3. C. NH₃S₂O₄
    4. D. N₂H₈SO₃
    [1]
16. 16.
    Ammonia burns in oxygen and the combustion, in the presence of a catalyst, may be represented by: $$2\mathrm{NH_3} + 2\frac{1}{2}\mathrm{O_2} \rightarrow 2\mathrm{NO} + 3\mathrm{H_2O}$$. What mass of steam, in grams, is produced when 1·5 g of nitrogen monoxide is formed?

    1. A. 0.90 g
    2. B. 1.35 g
    3. C. 2.70 g
    4. D. 4.05 g
    [1]
17. 17.
    Determine the molecular formula of a compound with the following percentage composition:

    Element	%	At. wt.	Relative no. of atoms	Simplest ratio
    B	86.64	11	7.87	3
    H	13.36	1	13.36	5

    Empirical formula: B₂H₅ Empirical formula weight: 38 Molecular weight: 112.29 What is the molecular formula of the compound?

    1. A. B₂H₅
    2. B. B₄H₁₀
    3. C. B₆H₁₅
    4. D. B₃H₇
    [1]
18. 18.
    The gases hydrogen, oxygen, carbon dioxide, sulphur dioxide, and chlorine are arranged in order of increasing relative molecular mass. If 8 g of each gas is taken at S.T.P., which gas will contain the least number of molecules and which the most?

    1. A. Cl₂ has the least, H₂ has the most
    2. B. SO₂ has the least, O₂ has the most
    3. C. CO₂ has the least, H₂ has the most
    4. D. O₂ has the least, Cl₂ has the most
    [1]
19. 19.
    0.5 gram of an organic compound contains 0.062 g of hydrogen and 0.25 g of oxygen. In the vapour state this compound weighs 32 times as heavy as the same volume of hydrogen. Determine the molecular formula of the compound.

    1. A. C₂H₄O
    2. B. C₂H₈O₂
    3. C. CH₄O
    4. D. C₄H₈O₄
    [1]
20. 20.
    10 g of a mixture of sodium chloride and anhydrous sodium sulphate is dissolved in water. An excess of barium chloride solution is added and 6.99 g of barium sulphate is precipitated according to the equation: Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl Calculate the percentage of sodium sulphate in the original mixture.

    1. A. 42.6%
    2. B. 50%
    3. C. 60%
    4. D. 30%
    [1]