Question

A certain mass of hydrogen gas collected over water at 10°C and 750mmHg pressure has a volume of 57cm3. Calculate the volume when it is dry at S.T.P ( S.V.P of water at 10°C = 9.2 mmHg .​

Answer 1

The volume of gas when it is dry at S.T.P : 53.6 cm³

Further explanation

Given

P tot=750 mmHg

V₁=57 cm³

T₁=10 °C = 283 K

P₂ = 760 mmHg(STP)

T₂ = 273 K(STP)

Required

P dry gas at STP

Solution

Dalton's Law

P tot = P H₂O + P gas

P gas = 750 mmHg - 9.2 mmHg

P gas = 740.8 mmHg = P₁

Combined gas Law

$\tt \dfrac{P_1.V_1}{T_1}=\dfrac{P_2.V_2}{T_2}\\\\V_2=\dfrac{P_1.V_1.T_2}{T_1.P_2}\\\\V_2=\dfrac{740.8\times 57\times 273}{283\times 760}=53.6~cm^3$