Question

When a certain amount of solid A is dissolved in 100 g of water at 25°C to make a dilute solution, the vapour pressure of the solution is reduced to one-half of that of pure water. The vapour pressure of pure water is 23.76 mmHg. The number of moles of solute A added is _________. (Nearest Integer).

Answer 1

$\frac{P_0-P_s}{P_s}$ =$\frac{n_A}{n_B}$
1 = $\frac{n_A}{n_B}$
nA-nB
∴ Moles of solute added considering it as a non- electrolyte
= $\frac{100}{18}$≈ 5.55
≈ 6