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

The standard emf of a galvanic cell with a Cd and Cr electrode in solutions of their respective 1.0 M nitrates at 25°C is 0.34 V.

Step-by-step explanation:

To determine 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, we must first identify the half-reactions taking place at each electrode and their standard reduction potentials (E°).

The standard half-cell potentials (available in standard reduction potential tables) for Cd2+ and Cr3+ are as follows:

The cathode is where reduction takes place, so the Cr3+ half-reaction will be the reduction (gain of electrons), and the Cd2+ half-reaction will be the oxidation at the anode (loss of electrons).

Next, we calculate the standard cell potential (E°cell) using the formula:

E°cell = E°cathode - E°anode

Since the Cr3+ half-reaction has the more negative standard reduction potential, it will be reversed to represent oxidation when it functions as the anode reaction. This gives us:

E°cell = (-0.40 V) - (-0.74 V) = 0.34 V

The positive standard cell potential indicates that the galvanic cell reaction is spontaneous under standard state conditions.

Answer 2

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