2) What is the pH of a 0.01 m solution of sodium acetate? Acetic acid is monopro

Question

2) What is the pH of a 0.01 m solution of sodium acetate? Acetic acid is monoprotic with an equilibrium like H (Ac 10 (HAC) You can assume that the sodium dissociates completely from the acetate and is not involved in any other important reactions a) Is this a conjugate base or an acid that you are adding to solution? b) Write down the Mass-Balance Relations, the Proton Balance Relation and the Equilibrium Relations c) Calculate the pH using both an analytic method, and by drawing the predominance diagram.

Explanation / Answer

2) sodium acetate is the salt of weak acid and strong base . only acetate ion will participate in hydrolysis

CH3COO- + H2O -------------------> CH3COOH + OH-

0.01 0 0 -------------------> initial

0.01-x x x -------------------> equilibrium

Kb = [CH3COOH][OH-]/[CH3COO-]

1.0 x 10^-14 / 1.8 x 10^-5 = x^2 / 0.01 -x

5.56 x 10^-10 = x^2 / 0.01 -x

x^2 + 5.56 x 10^-10 x - 5.56 x 10^-12 = 0

x = 2.36 x 10^-6

[OH-] = x = 2.36 x 10^-6

pOH = -log [OH-]

pOH = -log (2.36 x 10^-6)

pOH = 5.63

pH + pOH = 14

pH + 5.63 = 14

pH = 8.37

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