표준 환원 전위를 사용하여 CdS의 용해도곱 상수(Ks) 값 계산

표준 환원 전위를 사용하여 CdS의 용해도곱 상수(Ks) 값 계산

 

 

Electrochemical cell potentials can be used to determine equilibrium constants that would be otherwise difficult to determine because concentrations are small.

Calculate the value of Ksp for CdS at 298 K from the following data.

CdS(s) + 2e^- → Cd(s) + S^2-(aq) ... E° = -1.21 V

Cd^2+(aq) + 2e^- → Cd(s) ... E° = -0.40 V

 

A) 7.8×10^-12

B) 2.6×10^27

C) 3.9×10^-28

D) 3.2×10^18

 

 

Given the following E° values at 25℃, calculate Ksp for cadmium sulfide, CdS.

 

---------------------------------------------------

 

Cd(s) + S^2-(aq) → CdS(s) + 2e^-

Cd^2+(aq) + 2e^- → Cd(s)

------------------------------

Cd^2+(aq) + S^2-(aq) → CdS(s)

 

 

E° = (-0.40) - (-1.21) = +0.81 V

( 계산 설명 https://ywpop.tistory.com/4558 )

 

 

E° = RT/nF lnK

( 식 설명 https://ywpop.tistory.com/6519 )

 

lnK = E° / [RT/nF]

= 0.81 / [((8.314) (298)) / ((2) (96500))]

= 63.1

 

K = e^(63.1)

= 2.54×10^27

 

 

CdS(s) ⇌ Cd^2+(aq) + S^2-(aq)

 

Ksp = 1 / (2.54×10^27)

= 3.94×10^-28

 

 

답: C) 3.9×10^-28