The correct answer is 3. (a)-(i), (b)-(ii), (c)-(iv), (d)-(iii).
Let us break down the explanations for each part:
(a) Concentration of copper sulfate solution is doubled (i) EMF of the cell increases:
In the Daniell cell, the copper half-cell involves the reduction of copper ions (\(Cu^{2+}\) ions) to form copper metal at the copper electrode. If the concentration of the copper sulfate solution is doubled, it means there are more copper ions available for the reduction reaction. According to Le Chatelier's principle, an increase in the concentration of reactants favors the forward reaction. Therefore, doubling the concentration of the copper sulfate solution increases the rate of the reduction reaction, leading to an increase in the overall EMF (electromotive force) of the cell.
(b) Concentration of zinc sulfate solution is doubled (ii) EMF of the cell decreases:
In the zinc half-cell, zinc undergoes oxidation to form zinc ions (\(Zn^{2+}\)). If the concentration of the zinc sulfate solution is doubled, there are more zinc ions available for the oxidation reaction. According to Le Chatelier's principle, an increase in the concentration of reactants favors the forward reaction. Therefore, doubling the concentration of the zinc sulfate solution increases the rate of the oxidation reaction, leading to a decrease in the overall EMF of the cell.
(c) Concentrations of both solutions are doubled (iii) EMF of cell becomes equal to standard EMF:
Doubling the concentrations of both solutions affects both the reduction and oxidation reactions. However, if the concentrations of both solutions are doubled proportionally, the net effect on the EMF can be that it becomes equal to the standard EMF. This means that the system is moving towards equilibrium conditions, where the rates of the forward and reverse reactions are balanced, resulting in no net change in the cell potential.
(d) Concentrations of both solutions are kept equal (iv) No effect on EMF:
If the concentrations of both solutions are kept equal, it means there is no change in the concentration of reactants. Since the concentrations on both sides of the cell are balanced, there is no shift in equilibrium, and the rates of the oxidation and reduction reactions remain unchanged. As a result, there is no significant effect on the EMF of the cell.
In summary, changes in concentration affect the rates of the oxidation and reduction reactions in the Daniell cell, leading to changes in the overall cell potential (EMF). The detailed explanations above correspond to the correct matching in option (3). |
