What is pH of the solution when 100 ml of 0.1 molarity HCL is mixed with 100 ml of 0.1 molarity CH3cooh? (A)1 (B)2 (C)1.3 (D)2.3

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Answer 1 · 2018-06-19T12:50:51

We're adding a strong acid to a weakly acidic solution. The strong acid will dissociate completely and influence the equilibrium of the weak acid.

Consider,

#CH_3COOH rightleftharpoons CH_3COO^(-) + H^(+)#

puu.sh

where, #K_"a" = ([CH_3COO^-][H^+])/([CH_3COOH]) approx 1.8*10^-5#

Hence,

#K_"a" = (x(0.05+x))/(0.05-x) = 1.8*10^-5#

#=> x approx 1.8*10^-5#

and by extension,

#"pH" = -log(0.05+x) approx 1.30" "("C")#