Derive an expression for the degree of hydrolysis of NH 4 Cl. - Wired Faculty

Equilibrium

Question

Derive an expression for the degree of hydrolysis of NH₄Cl.

Solution

Hydrolysis of NH₄Cl can be represented as

NH subscript 4 superscript plus

+ H₂O

rightwards harpoon over leftwards harpoon

NH₄OH + H⁺
Initial conc.
c 0 0

Equilibrium conc .

straight c left parenthesis 1 minus straight alpha right parenthesis

cα

cα

straight K subscript straight h space equals space fraction numerator cα space cross times space cα over denominator straight c left parenthesis 1 minus straight alpha right parenthesis end fraction space equals space fraction numerator cα squared over denominator 1 minus straight alpha end fraction

Since

straight alpha

is very small as compared to unity,

therefore space space space space space 1 minus straight alpha space equals space 1 space space space space space space space space straight K subscript straight b space space equals space cα squared or space space space space space space straight alpha squared space equals space straight K subscript straight h over straight c or space space space space space space space straight alpha space equals space square root of straight K subscript straight h over straight K subscript straight b end root But space space space straight K subscript straight h space equals space straight K subscript straight w over straight K subscript straight b therefore space space space space space straight alpha space equals space square root of fraction numerator straight K subscript straight w over denominator straight K subscript straight b space cross times space straight c end fraction end root

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