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Question

The mass of 11.2 L of NH₃ gas at S.T.P. is:

[N = 14, H = 1]

(a) 17 g

(b) 8.5 g

(c) 34 g

(d) 11.2 g

WBBSE Class X Physical Science Behaviour of Gases 01 Mark 2026

Answer

(b) 8.5 g

Explanation

At S.T.P., 1 mole of any gas occupies 22.4 L.

Therefore, 11.2 L of NH₃ = \frac{11.2}{22.4} = 0.5 mol

Molar mass of NH₃ = 14 + (1 × 3) = 17 g/mol

Mass of 0.5 mol NH₃ = 0.5 × 17 = 8.5 g

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