Question

CuSO${}_4.$5$H_{2}O$(s) $\rightleftharpoons$ CuSO${}_4$.3H${}_{2}O$(s) + 2H${}_{2}O$(g); $k_p$ = 4 ${10}^4$ atm${}^2.$ If the vapour pressure of water is 38 torr then percentage of relative humidity is : (Assume all data at constant temperature)

• A. 4
• B. 10
• C. 40
• D. None of these

Answer 1

The correct option is C 40

$\begin{array}{cc}{K}_P& ={\left(P_{H_{2}O}\right)}^2\\ P_{H_{2}O}& =\sqrt{K_P}\\ & =\sqrt{4\times {10}^{-4}}\\ & =2\times {10}^{-2}\end{array}$

$\text{\% Relative Humidity}=\frac{P_{H_{2}O}\times 760}{\text{v.p of water}}$

$\begin{array}{cc}=& \frac{2\times {10}^{-2}\times 760\times 100}{38}\\ & =40\end{array}$