Question

Calculate the degree of ionization and pH of 0.05 M ammonia solution. The ionization constant of ammonia (Kb) is 1.77 × $10^{-5}$. Also calculate the ionic constant of the conjugate acid of ammonia.

Answer 1

i) To calculate degree of ionization

Given, Concentration = 0.05 M

Ionization constant, ${ K }_{ b }\quad =\quad 1.77\quad \times \quad { 10 }^{ -5 }$

We know that, ${ K }_{ b }\quad =\quad C{ \alpha }^{ 2 }$

Where, C = concentration

$\alpha \quad =\quad Degree\quad of\quad ionization$

Then, $\alpha \quad =\quad \frac { \sqrt { 1.77\quad \times \quad { 10 }^{ -5 } } }{ 0.05 }$

$\alpha \quad =\quad 0.0188$

ii ) To calculate pH  

$pH\quad =\quad C\alpha$  

$=\quad 0.05\quad \times \quad 0.0188$

$pH\quad =\quad 9.4\quad \times \quad { 10 }^{ -4 }\quad M$

$pOH\quad =\quad -\log { 9.4\quad \times \quad { 10 }^{ -4 } } \quad =\quad 3.0$

Therefore, $pH\quad =\quad 14\quad -\quad 3\quad =\quad 11$