methylamine Henderson-Hasselbalch pH [CH3NH2]/[CH3NH3^+]

methylamine Henderson-Hasselbalch pH [CH3NH2]/[CH3NH3^+]

 

 

메틸아민 용액에 대한 Henderson-Hasselbalch 식을 쓰시오.

다음의 pH에서 [CH3NH2]/[CH3NH3^+]의 비를 계산하시오.

a) pH 4.00

b) pH 10.632

c) pH 12.00

 

 

Write the Henderson-Hasselbalch equation for a solution of methylamine.

Calculate the quotient [CH3NH2]/[CH3NH3^+] at

a) pH 4.00

b) pH 10.632

c) pH 12.00

 

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The Kb for methylamine, CH3NH2, at 25℃ is 4.4×10^(-4)

 

pKb = -logKb

= -log(4.4×10^(-4)) = 3.3565

 

 

 

Henderson-Hasselbalch 일반식

pOH = pKb + log([짝산]/[약염기])

( 참고 https://ywpop.tistory.com/1926 )

 

pOH = pKb – log([약염기]/[짝산])

 

log([약염기]/[짝산]) = pKb – pOH

 

[약염기]/[짝산] = 10^(pKb – pOH)

 

[CH3NH2]/[CH3NH3^+] = 10^(pKb – pOH)

 

 

 

 

a) pH 4.00

 

pOH = 14.00 – pH

= 14.00 – 4.00 = 10.00

 

 

[CH3NH2]/[CH3NH3^+] = 10^(3.3565 – 10.00)

= 2.27×10^(-7)

 

 

 

 

b) pH 10.632

 

pOH = 14.00 – 10.632 = 3.368

 

 

[CH3NH2]/[CH3NH3^+] = 10^(3.3565 – 3.368)

= 0.974

 

 

 

 

c) pH 12.00

 

pOH = 14.00 – 12.00 = 2.00

 

 

[CH3NH2]/[CH3NH3^+] = 10^(3.3565 – 2.00)

= 22.7