Question

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]

Options

• 1 and 2

• 1 and 3

• 2 and 3

• 1, 2 and 3

Answer 1

1 and 3

Explanation:

Gram molecular = 1 mole

= 6.022 × 10²³ molecules

= 22.4 L

∴ Molecular Mass of \[\ce{O2}\] gas = 32 g

= 6.022 × 10²³ molecules

= 22.4 L

Similary, 6.022 × 10²³ molecule of \[\ce{NH3}\] = 22.4 L

Since 1 mole of any gas occupies 22.4 litres at STP, 2 moles of hydrogen gas would occupy 2 × 22.4 = 44.8 litres, which is more than 22.4 litres.