Question

1) For the reaction 2Co3+(aq)+2Cl−(aq)→2Co2+(aq)+Cl2(g). E∘=0.483 V what is the cell potential at 25 ∘C if the concentrations are[Co3+]= 0.685 M , [Co2+]= 0.417 M , and [Cl−]= 7.70×10⁻²M and the pressure of Cl2 is PCl2= 6.60 atm ?

2)Part A

At 63.0 ∘C , what is the maximum value of the reaction quotient, Q , needed to produce a non-negative E value for the reaction

SO42−(aq)+4H+(aq)+2Br−(aq)⇌Br2(aq)+SO2(g)+2H2O(l)

In other words, what is Q when E=0 at this temperature?Express your answer numerically to two significant figures.

Answer 1

1)

Ecell = E0cell - 0.0591/nlog[Cl2][Co2+]^2/[Cl-]^2[Co3+]^2

n = no of electrons transfered = 2

E0cell = 0.483 V

[Co3+]= 0.685 M , [Co2+]= 0.417 M , and [Cl−]= 7.70×10−2 M

the pressure of Cl2 is PCl2= 6.60 atm

Ecell = 0.483 - (0.0591/2)log((6.6*0.417^2)/(0.077^2*0.685^2))

      = 0.4 V

2) E0cell = E0cathode - E0anode

           =   0.17 - 1.066

           = -0.896 V

Ecell = E0cell - 2.303RT/nFlogQ

     0 = -0.896 - ((2.303*8.314*336.15)/(2*96500))logQ

Q = reaction quotient = 1.356*10^-27    = 1.4*10^-27