By Sunil Bhardwaj

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Calculate the degree of ionization and the hydroxyl ion concentration in \(0.2M N{ H }_{ 3 }\) solution \(({ K }_{ b } = 1.85 \times { 10 }^{ -5 } at \ 298K).\)

Ans: Degree of ionization is given by, $$ \alpha = \sqrt { \frac { { K }_{ b } }{ C } } $$ $$ = \sqrt { \frac { 1.85 \times { 10 }^{ -5 } }{ 0.2 } } $$ $$= 0.925 \times { 10 }^{ -3 }$$ for the ionization reaction,$$ \underset { C\left( 1-\alpha \right) }{ N{ H }_{ 3 } } + { H }_{ 2 }O \rightleftharpoons \underset { C\alpha }{ N{ { H }_{ 4 } }^{ + } } + \underset { C\alpha }{ { OH }^{ - } } $$ $$ \left[ { OH }^{ - } \right] = C\alpha = 0.2 \times 0.925 \times { 10 }^{ -3 } $$ $$= 0.185 \times { 10 }^{ -3 }M $$