0.20 M CrO4^2-, 0.10 M CO3^2-, 0.010 M Cl^- AgNO3

0.20 M CrO4^2-, 0.10 M CO3^2-, 0.010 M Cl^- AgNO3

 

 

A solution contains three anions with the following concentrations:

0.20 M CrO4^2-, 0.10 M CO3^2-, 0.010 M Cl^-.

If a dilute AgNO3 solution is slowly added to the solution,

what is the first compound to precipitate:

Ag2CrO4 Ksp = 1.2×10^(-12)

Ag2CO3 Ksp = 8.1×10^(-12)

AgCl Ksp = 1.8×10^(-10)

 

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▶ 참고: Ksp [ https://ywpop.tistory.com/2966 ]

▶ 참고: 난용성염의 용해도와 공통이온효과

[ https://ywpop.tistory.com/3141 ]

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Ag2CrO4(s) ⇌ 2Ag^+(aq) + CrO4^2-(aq)

Ksp = [Ag^+]^2 [CrO4^2-]

 

 

[Ag^+]^2 = Ksp / [CrO4^2-]

 

[Ag^+] = [Ksp / [CrO4^2-]]^(1/2)

= [(1.2×10^(-12)) / (0.20)]^(1/2)

= 2.45×10^(-6) M

 

 

 

 

Ag2CO3(s) ⇌ 2Ag^+(aq) + CO3^2-(aq)

Ksp = [Ag^+]^2 [CO3^2-]

 

 

[Ag^+]^2 = Ksp / [CO3^2-]

 

[Ag^+] = [Ksp / [CO3^2-]]^(1/2)

= [(8.1×10^(-12)) / (0.10)]^(1/2)

= 9.0×10^(-6) M

 

 

 

 

AgCl(s) ⇌ Ag^+(aq) + Cl^-(aq)

Ksp = [Ag^+] [Cl^-]

 

 

[Ag^+] = Ksp / [Cl^-]

= (1.8×10^(-10)) / (0.010)

= 1.8×10^(-8) M

 

 

 

 

가장 작은 값의 [Ag^+]가 답이므로,

답: AgCl

 

 

 

[ 관련 예제 https://ywpop.tistory.com/15977 ] 1.0×10^(-4) M Cu^+ and 2.0×10^(-3) M Pb^2+

 

 

 

[키워드] 먼저 침전 기준문서, precipitate first 기준문서