Question

One litre flask contains air, water vapour and small amount of liquid water at a pressure of 200 mm Hg. If this is connected to another one litre evacuated flask, what will be the final pressure of the gas mixture at equilibrium?

Assume the temperature to be 50${}^o$ C. (Aqueous tension at 50${}^o$ C = 93 mm Hg).

• A. 120.56 mm
• B. 230 mm
• C. 146.5 mm
• D. 109.4 mm

Answer 1

Answer: (C)

146.5 mm

$P_T=200$ mm Hg

$P_{H_{2}O}=93$ mm Hg

$P_1=200mmHg-93mmHg=107mmHg$

We know, $PV=K$ at constant T.

$P_1{V}_1=P_2{V}_2$

$107\times 1=P_2\times 2$

$P_2=53.5$ mm Hg

$P_{mix}=(53.5+93)$ mmHg $=146.5$ mm Hg

Hence, the correct option is $\text{C}$.