Question

$pH$ of a $0.1$ M monobasic acid is measured to be $2$. Its osmotic pressure at given temperature $TK$ is:

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

Answer 1

The correct option is B $0.11$ RT

Given that;

$pH=2;\left[HA\right]=0.1M$

$\Rightarrow \left[H^{+}\right]=0.01M$

$HA\leftrightharpoons H^{+}+A^{-}$

$0.1(1-\alpha )$ $0.1\alpha$ $0.1\alpha$

Now,

$0.1\alpha =0.01\Rightarrow \alpha =0.1$

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

Again.

$\pi =iMRT$

where,

$\pi$ is osmatic pressure.

M is the molar concentration of dissolved species (units of mol/L).

R is the ideal gas constant (0.08206 L atm mol${}^{-1}$ K${}^{-1}$.

T is the temperature on the Kelvin scale.

$\pi =1.1\times 0.1\times RT=0.11RT$

Hence option B is correct.