Question

$pH$ of a $0.1M$ monobasic acid is found to be $2$. Hence its osmotic pressure at a given temp. $TK$ is:

• A. $0.1RT$
• B. $0.11RT$
• C. $1.1RT$
• D. $0.01RT$

Answer 1

The correct option is B $0.11RT$

$pH=2$

According to Arrhenius principle.

$pH=-log\left[H^{+}\right]$

$2=-log\left[H^{+}\right]$

$\left[H^{+}\right]=\mathrm{0.01.}$

Assume HX is a mono basic acid.

$HX\rightleftharpoons H^{+}+X^{-}$

Relation $b/w\left[H^{+}\right]$ & degree of dissociation

$\left[H^{+}\right]=c\alpha$

$\frac{0.01}{0.1}=\alpha$

$\alpha \Rightarrow 0.1$

Now, According to vant Hoff's principle,

$i=1+\alpha$

$i=1+0.1\Rightarrow i=1.1$

Osmotic pressure $\prod =iCRT$

$\prod =1.1\times 0.1\times RT$

$\prod =0.11RT$

Hence, the correct option is $B$