Question

26.An electrochemical cell is constructed with two Ni(s) electrodes, each in a cell containing Ni2*(aq). Electrons flow through the wire connecting the electrodes from the left hand compartment to the right hand compartment. What can be said about the overall cell? a. [Ni2 in the right compartment <[N2] in the left compartment b. Ni in the right compartment> [Ni in the left compartment C. [Ni] in the right compartment d. More info is needed. = [NF+] in the left compartment
Apparently the correct answer was not c but b. Can someone please explain why? Thank you

Answer 1

this is concentration cell. in both compartments Ni2+ solution is present .

let us see clear reactions:

anode reaction (left ) : Ni (s) --------------------> Ni2+ (aq , C1 ) + 2e-

cathode reaction (right) + Ni2+ (aq , C2 ) + 2e- ----------------> Ni (s)

overall reaction : Ni2+ (aq , C2 ) ---------------> Ni2+ (aq , C1 )

note that here C1 and C2 are different concentrations

from nernest equation :

Ecell = Eocell - 0.05916 / n * log [anode concentration / cathode concentration ]

Eocell = 0 because both cells have same electrodes

Ecell = 0 - 0.05916 / n * log [anode concentration / cathode concentration ]

Ecell = - 0.05916 / n * log [anode concentration / cathode concentration ]

Ecell = 0.05916 / n * log [cathode concentration / anode concentration ]

for spontaneous cell reaction   Ecell should be positive   for this   cathode concentration > anode concentration

that means C2 > C1

right compartment concentration > left compartment concentration

so correct answer is b)