pH 4.00 buffer 0.20 M C6H5COOH C6H5COONa

pH 4.00 buffer 0.20 M C6H5COOH C6H5COONa

pH 4.00 buffer 제조할 때,

0.20 M C6H5COOH 용액에 존재하는

C6H5COONa의 농도 계산

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> Ka for benzoic acid is 6.5×10^(-5)

> Ka for benzoic acid is 6.3×10^(-5)

---> pKa = –log(6.3×10^(-5)) = 4.2

Henderson-Hasselbalch 식

pH = pKa + log([짝염기]/[약산])

( 참고 https://ywpop.tistory.com/1926 )

log([짝염기]/[약산]) = pH – pKa

[짝염기] / [약산] = 10^(pH – pKa)

[짝염기] = 10^(pH – pKa) × [약산]

= 10^(4.00 – 4.2) × [0.20]

= 0.1262 M

답: 0.13 M

[검산]

pH = 4.2 + log(0.1262 / 0.20) = 4.00

[키워드] 벤조산 완충용액의 pH 기준