Question

A box contains 0.90 g of liquid water in equilibrium with water vapour at 27°C. The equilibrium vapour pressure of water at 27°C is 32.0 Torr. When the volume of the box is increased, some of the liquid water evaporates to maintain the equilibrium pressure.
If all the liquid water evaporates, then the volume of the box must be ______ litre. [nearest integer]
(Given : R = 0.082 L atm K–1 mol–1] (Ignore the volume of the liquid water and assume water vapours behave as an ideal gas.)

Answer 1

The correct answer is 29
$H_2O(l) ⇆ H_2O(g)$
$t = t_{eg} \frac{0.90}{18} - x$ $x$
Pv = nRT
$\frac{32}{760} × V = 0.082 × (x) × 300$
$x = \frac{0.90}{18}$
$V = 0.082 × \frac{0.90}{18} × 300×\frac{760}{32}$
$≈ 29.21 L$
$≈ 29L$