1(xiii)
Which of the following would occupy 22.4 litres at S.T.P.?
(1) 32g of oxygen gas
(2) 2 moles of hydrogen gas
(3) 6.022 x 1023 molecules of ammonia
- (a)1 & 2
- (b)1 & 3
- (c)2 & 3
- (d)1, 2 & 3
[Atomic weights: O = 16, H = 1, N = 14]
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1 & 3
Reason — (1) The molar mass of O2 = 2 × atomic mass of oxygen ≈ 32 g/mol.
So, 32 grams of O2 is equivalent to 1 mole of O2. 1 mole of any gas at S.T.P. occupies 22.4 liters.
(2) 2 moles of hydrogen gas will occupy 2 x 22.4 = 44.8 litres
(3) 1 mole of NH3 contains 6.022 × 1023 molecules and occupies 22.4 liters at S.T.P. Therefore, 6.022 × 1023 molecules of NH3 will also occupy 22.4 liters at S.T.P.