Acetic acid and propionic acid have K a values 1.75 × 10 - 5 and 1 .3 × 10 − 5 respectively at a certain temperature. An equimolar solution of a mixture of the two acids is partially neutralized by NaOH. How is the ratio of the contents of acetate and propionate ions related to the K a values and the molarity ?

Question

Acetic acid and propionic acid have K a values 1.75 × 10 - 5 and 1 .3 × 10 − 5 respectively at a certain temperature. An equimolar solution of a mixture of the two acids is partially neutralized by NaOH. How is the ratio of the contents of acetate and propionate ions related to the K a values and the molarity ?, α 1 - α = 1.75 1.3 × β 1 - β , where α and β are ionized fractions of the acids, The ratio is unrelated to the K a values, The ratio is unrelated to the molarity, The ratio is unrelated to the pH of the solution

MARKS App · Accepted Answer

In a given mixture, the ionization of two acids can be written as : Let α , β be degree of ionization at same concentration. C H 3 C O O H 1 - α ⇌ C H 3 C O O - + α H + α + β C 2 H 5 C O O H 1 - β ⇌ C 2 H 5 C O O - + β H + α + β ∴ K Acetic acid = α α + β ·c 1 − α K Propionic acid = β α + β ⋅ c 1 − β ∴ K Acetic acid K Propionic acid = α 1 − α × 1 − β β or α 1 - α = 1 · 75 1 · 3 × β 1 - β

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