0.1 M chloroacetic acid 용액의 pH. pKa = 2.86

0.1 M chloroacetic acid 용액의 pH. pKa = 2.86

0.1 M ClCH2COOH 용액의 pH. pKa = 2.86

 

 

What is the pH of a 0.1 M solution of chloroacetic acid?

(ClCH2COOH, pKa = 2.86)

 

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pKa = -logKa = 2.86

Ka = 10^(-2.86) = 0.00138

 

 

 

x = [Ka × C]^(1/2) = [H^+]

pH = -log[H^+]

( 참고 https://ywpop.tistory.com/4294 )

 

 

 

x = [0.00138 × 0.1]^(1/2)

= 0.01175 M = [H^+]

 

0.1 M × (5/100) = 0.005 M < 0.01175 M

---> 5% 검증 실패.

 

 

 

x^2 / (0.1 – x) = 0.00138

x^2 + 0.00138x – 0.000138 = 0

 

근의 공식으로 x를 계산하면,

( 참고 https://ywpop.tistory.com/3302 )

 

x = 0.01108 M = [H^+]

 

 

 

pH = -log[H^+]

= -log(0.01108)

= 1.96

 

 

 

답: pH = 1.96