Question

What is the standard emf of a galvanic cell made of a cd electrode in a 1.0 m cd(no3)2 solution and a cr electrode in a 1.0 m cr(no3)3 solution at 25°c?

Answer 1

Standard reduction potential of Cd2+ = -0.403 v
Standard reduction potential of Cr3+ = -0.74 v

Here, reduction potential of Cd2+ is higher as compared to Cr3+. Hence, it will preferentially undergo reduction. 

The electrochemical cell is represented as
Cr/Cr3+// Cd2+/Cd

Now, standard EMF of cell = E = ECd2+/Cd - ECr3+/Cr  
                                                  = - 0.403. - (-0.74)
                                                  = 0.337 v