약산과 약염기: 0.060 M solution of trimethylammonium chloride

약산과 약염기: 0.060 M solution of trimethylammonium chloride

 

 

0.060 M 염화트라이메틸암모늄 용액에서 pH와 (CH3)3N, (CH3)3NH+의 농도를 구하시오.

0.06 M 염화트리메틸암모늄 용액의 pH를 구하고 (CH3)3N과 (CH3)3NH+의 농도를 구하시오.

 

Find the pH and concentrations of (CH3)3N and (CH3)3NH+ in a 0.060 M solution of trimethylammonium chloride?

 

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	(CH3)3NH+	⇌	(CH3)3N	+	H+
초기:	0.060		0		0
변화:	-x		+x		+x
평형:	0.060-x		x		x

 

(CH3)3NH+의 Ka = 1.58×10^-10

Ka = [(CH3)3N][H+] / [(CH3)3NH+]

= (x)(x) / (0.060-x)

 

(CH3)3NH+가 약산이므로 (상당히 작은 Ka값),

x값이 매우 작다고 보고, 근사적으로 계산하면,

즉 0.060-x ≒ 0.060

 

x^2 = Ka × 0.060

x = 3.08×10^-6

 

[(CH3)3N] = [H+] = 3.08×10^-6 M

[(CH3)3NH+] ≒ 0.060 M

 

pH = -log[H+] = -log(3.08×10^-6) = 5.51