In the electrochemical reaction, `2Fe^(3+)+Zn rarr Zn^(2+) + 2Fe^(2+)` increasing the concentration of `Fe^(2+)`:

Options

A. increases the cell emf
B. increases the current flow
C. decreases the cell emf
D. alters the pH of the solution

Answer

To solve the problem regarding the electrochemical reaction `2Fe^(3+) + Zn → Zn^(2+) + 2Fe^(2+)`, we will analyze the effects of increasing the concentration of `Fe^(2+)` on the cell's emf (electromotive force), current flow, and pH of the solution.

### Step-by-Step Solution:

1. **Identify the Reaction**: The given reaction involves the reduction of `Fe^(3+)` to `Fe^(2+)` and the oxidation of `Zn` to `Zn^(2+)`.

2. **Use Nernst Equation**: The Nernst equation is used to calculate the emf of the cell under non-standard conditions:
\[ E = E^\circ - \frac{0.059}{n} \log \left( \frac{[Fe^{2+}]^2 [Zn^{2+}]}{[Fe^{3+}]^2 [Zn]} \right) \]
where:
- \(E^\circ\) is the standard electrode potential,
- \(n\) is the number of electrons transferred (which is 2 in this case),
- \([Fe^{2+}]\), \([Zn^{2+}]\), \([Fe^{3+}]\), and \([Zn]\) are the concentrations of the respective species.

3. **Effect of Increasing [Fe^(2+)]**: When the concentration of `Fe^(2+)` increases, the term \([Fe^{2+}]^2\) in the Nernst equation increases. This leads to an increase in the logarithmic term:
\[ \log \left( \frac{[Fe^{2+}]^2 [Zn^{2+}]}{[Fe^{3+}]^2 [Zn]} \right) \]
Since the logarithm of a larger number is greater, this will cause the overall value of the logarithmic term to increase.

4. **Impact on E**: As the logarithmic term increases, the term \(-\frac{0.059}{n} \log\) becomes more negative, which means that the overall emf \(E\) of the cell decreases:
\[ E = E^\circ - \text{(a larger positive value)} \]
Thus, the emf of the cell decreases.

5. **Current Flow**: The current flow in an electrochemical cell is directly related to the emf. If the emf decreases, the driving force for the reaction decreases, which typically results in a decrease in the current flow.

6. **Effect on pH**: The reaction produces `Fe^(2+)`, which can lead to a decrease in pH (increase in acidity) as more `Fe^(2+)` ions are present in the solution. However, the exact change in pH would depend on the buffering capacity of the solution and the extent of the reaction.

### Conclusion:
- The increase in concentration of `Fe^(2+)` leads to a decrease in the cell emf.
- The current flow will also decrease as a result of the decreased emf.
- The pH of the solution may decrease due to the increase in `Fe^(2+)` concentration.

### Final Answer:
The overall effect of increasing the concentration of `Fe^(2+)` is that the cell emf decreases.