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Question: \(K_{a}\)for \(CH_{3}COOH\) is \(1.8 \times 10^{- 5}\)and \(K_{b}\) for \(NH_{4}OH\) is \(1.8 \times...

KaK_{a}for CH3COOHCH_{3}COOH is 1.8×1051.8 \times 10^{- 5}and KbK_{b} for NH4OHNH_{4}OH is 1.8×1051.8 \times 10^{- 5}The pH of ammonium acetate will be.

A

7.0057.005

B

4.754.75

C

7.07.0

D

Between 6 and 7

Answer

7.07.0

Explanation

Solution

: CH3COONH4CH_{3}COONH_{4} is a salt of weak acid (CH3COOH)(CH_{3}COOH) and weak base (NH4OH).(NH_{4}OH).

pH=7+12(pKapKb)pH = 7 + \frac{1}{2}(pK_{a} - pK_{b})

pKa=logKa=log(1.8×105)=4.74pK_{a} = - \log{}K_{a} = - \log{}(1.8 \times 10^{- 5}) = 4.74

pKb=logKb=log(1.8×105)=4.74pK_{b} = - \log{}K_{b} = - \log{}(1.8 \times 10^{- 5}) = 4.74

pH=7+12(4.744.74)=7.0pH = 7 + \frac{1}{2}(4.74 - 4.74) = 7.0