We are being asked to calculate the pH of a 0.40 M solution of sodium acetate (NaCH3COO) given that the Ka of acetic acid (CH3COOH) is 1.8 x 10-5.
NaCH3COO is a salt and it will break up in the solution:
NaCH3COO → Na+(aq) + CH3COO-(aq)
CH3COO- is the conjugate base of a weak acid (CH3COOH):
CH3COOH + H2O(l) → CH3COOH-(aq) + H3O+(aq)
(weak acid) (conjugate base)
Since we’re dealing with a weak base, we will have to create an ICE chart to determine the equilibrium concentration of each species:
• CH3COO- → weak base → proton acceptor
• H2O → will act as the weak acid → proton donor
Equilibrium reaction: CH3COO-(aq) + H2O(l) ⇌ CH3COOH(aq) + OH-(aq)
Calculate the pH of a 0.40 M solution of sodium acetate (NaCH3COO) given that the Ka of acetic acid (CH3COOH) is 1.8 x 10-5.
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What scientific concept do you need to know in order to solve this problem?
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