Consider a galvanic cell based upon the following half reactions: Ni2+ + 2e- Ni

Question

Consider a galvanic cell based upon the following half reactions:

Ni2+ + 2e- Ni -0.27 V

Cr3+ + 3e- Cr -0.73 V

How many of the following responses are true?

1. Adding equal amounts of water to both half reaction vessels will decrease the potential of the cell

2. Increasing the mass of the Ni will change the initial potential of the cell

3. Cr is being oxidized during the reaction

4. Decreasing the concentration of Ni2+ (assuming no volume change) will decrease the potential of the cell

5. Decreasing the concentration of Cr3+ (assuming no volume change) will decrease the potential of the cell

Explanation / Answer

1. Adding equal amounts of water to both half reaction vessels will decrease the potential of the cell

Adding water decreasess concnetration

Ecell = E°cel - 0.0592/n*log(Q) --- > Q product s/ reactants and we know that Cr+3 goes on top and Ni+2 goes down, therefore, decreasing concnetrations, will affect the most Q; it will decrease

2. Increasing the mass of the Ni will change the initial potential of the cell

True, since you favour Ni+ formation due to lechatelier principle

3. Cr is being oxidized during the reaction

true, sinc th epotential is the most negative

4. Decreasing the concentration of Ni2+ (assuming no volume change) will decrease the potential of the cell

False, it increase the value of Q, then Ecell increases

5. Decreasing the concentration of Cr3+ (assuming no volume change) will decrease the potential of the cell

True, increasing Cr+3 decreases Q, thereofre decreases logQ; and Ecell

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