Q1: The emf of a Deniell cell  can be increased by

ANS:D - increasing the concentration of copper sulphate solution.

The emf (electromotive force) of a Daniell cell can be increased by increasing the concentration of copper sulfate solution. Explanation:

1. Daniell Cell: The Daniell cell is an electrochemical cell that consists of a zinc electrode immersed in a zinc sulfate solution and a copper electrode immersed in a copper sulfate solution. These solutions are connected by a salt bridge, allowing ions to flow and completing the circuit.
2. Emf of the Daniell Cell: The emf of the Daniell cell depends on the potential difference between the two half-cells, which is influenced by the concentration of the solutions and the types of electrodes used.
3. Effect of Solution Concentration: Increasing the concentration of copper sulfate solution increases the concentration of copper ions in the solution. This leads to a higher concentration of copper ions available for reduction at the copper electrode during the cell reaction (Cu^2+ + 2e^- -> Cu). As a result, the reduction reaction proceeds more readily, leading to a higher potential at the copper electrode and an increase in the emf of the cell.
4. Effect of Electrode Surface Area: While increasing the surface area of the electrodes can affect the rate of reaction and the current capacity of the cell, it does not directly influence the emf of the cell. Therefore, options mentioning changes in electrode surface area do not contribute to increasing the emf of the Daniell cell.
5. Effect of Zinc Sulfate Concentration: Increasing the concentration of zinc sulfate solution would lead to an increase in the concentration of zinc ions in the solution. However, this would not directly affect the emf of the cell, as the emf primarily depends on the concentration of the copper sulfate solution in the Daniell cell.