What is the pH of a 0.01 m solution of sodium acetate? What is the PH of a 0.01

Question

What is the pH of a 0.01 m solution of sodium acetate?

What is the PH of a 0.01 m solution of sodium acetate? Acetic acid is monoprotic with an equilibrium like: HAc = H^+ + Ac^- K_a1 = 10^-4.7 = (H^+) (Ac^-)/(HAc) you can assume that the sodium dissociates completely from the acetate and is not involved in any other important reactions. Is this a conjugate base or an acid that you are adding to solution? Write down the Mass-Balance Relations, the Proton Balance Relation and the Equilibrium Relations. Calculate the pH using both an analytic method, and by drawing the predominance diagram.

Explanation / Answer

What is the pH of a 0.01 m solution of sodium acetate

AcNa = Ac- + Na+

Here AcNa = 0.01

Ac- = 0.01

Ac- + H2O ~~> OH + AcH

Kb = [OH-][AcH]/[Ac-]

Kb=10^-14/Ka

= 10^-14/1.8*10^-5

= 5.556x10^-10

[OH-]______[AcH]________[Ac-]
initial_____0_______0_________1M
change___+x______+x_________-x
final______x_______x__________1-x

Kb = x^2/(0.01-x) = 5.556x10-10

5.556x10^-10 = x^2/(0.01-x)

5.556x10^-12 -5.556x10^-10x = x^2

x^2+5.556x10^-10x -5.556x10^-12= 0

Solve for x:

x=0.000 002 3661

=2.36e-6 M = [OH-]
pOH = -log[OH] = 5.63
pH=14-pOH=8.37

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