a. What is the pH of a 1.14 M solution of CH 3 COOH that is also 0.65 M in galli
ID: 713003 • Letter: A
Question
a. What is the pH of a 1.14 M solution of CH3COOH that is also 0.65 M in gallium acetate, the salt of it's conjugate base? The Ka for CH3COOH = 1.8 X 10-5.
b. In one flask you are given 160.0 mL of a 6.20 M solution of hypochlorous acid. In a separate flask you are given 280.0 mL of a 0.70 M solution of gallium hypochlorite. What is the final pH when these two flasks are mixed together and allowed to equilibrate? The Ka for hypochlorous acid = 2.9 X 10-8
c. What is the pH of a 0.457 M solution of potassium fluoride? Ka for HF = 7.1 X 10-4.
Explanation / Answer
a) pH=pka+log [base]/[acid] (henderson-hasselbach equation)
Here CH3COOH is the acid and acetate ,CH3COO- is its conjugate bae.
[CH3COOH]=1.14M
(CH3COO)3Ga--->3CH3COO- +Ga3+
[CH3COO-]=3[gallium acetate]=3*0.65M=1.95M
ka=1.8*10^-5
pka=-log ka=-log (1.8*10^-5)=4.7
pH=4.7+log (1.95/1.14)=4.9
pH=4.9
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