By Sunil Bhardwaj

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Calculate the degree of ionization and the hydrogen ion concentration of a \({ 10 }^{ -3 }M\) acetic acid solution at 298 K \(({ K }_{ a } = 1.85 \times { 10 }^{ -5 })\).

Ionization reaction for acetic acid is $$ \underset { C\left( 1-\alpha \right) }{ C{ H }_{ 3 }COOH } \rightleftharpoons \underset { C\alpha }{ C{ H }_{ 3 }CO{ O }^{ - } } + \underset { C\alpha }{ { H }^{ + } } $$ $$ C = { 10 }^{ -3 }M { K }_{ a } = 1.85 \times { 10 }^{ -5 } $$ from the formula, $$ \alpha = \sqrt { \frac { { K }_{ a } }{ C } } $$ $$ = \sqrt { \frac { 1.85 \times { 10 }^{ -5 } }{ { 10 }^{ -3 } } } $$ $$= \sqrt { 0.0185 } = 0.136 $$ Hydrogen ion concentration can be given as, $$ \left[ { H }^{ + } \right] = C{ \alpha } = 0.136 \times { 10 }^{ -3 } M $$