Daniel cell, the EMF of the cell can b e increased b y

Options

A. increasing the concentration of `Zn^(2+)` ions
B. increasing the concentration of `Cu^(2+)` ions
C. increasing the concentration of `Cu^(2+)` ions
D. decreasing the concentration of `Zn^(2+)` ions.

Explanation

To solve the question regarding how to increase the EMF (Electromotive Force) of a Daniel cell, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Daniel Cell:**
The Daniel cell consists of two half-cells: one with zinc (anode) and one with copper (cathode). The overall reaction involves the oxidation of zinc and the reduction of copper ions.

2. **Know the Nernst Equation:**
The EMF of the cell can be calculated using the Nernst equation:
\[ E_{\text{cell}} = E^\circ_{\text{cell}} - \frac{0.0591}{n} \log \left(\frac{[\text{Zn}^{2+}]}{[\text{Cu}^{2+}]}\right) \]
where \(E^\circ_{\text{cell}}\) is the standard EMF, \(n\) is the number of moles of electrons transferred, and \([\text{Zn}^{2+}]\) and \([\text{Cu}^{2+}]\) are the concentrations of zinc and copper ions, respectively.

3. **Identify the Factors Affecting EMF:**
To increase the EMF (\(E_{\text{cell}}\)), we need to manipulate the terms in the Nernst equation. Specifically, we want to decrease the value of the logarithmic term.

4. **Manipulate Concentrations:**
The logarithmic term is:
\[ \log \left(\frac{[\text{Zn}^{2+}]}{[\text{Cu}^{2+}]}\right) \]
To decrease this term, we can either:
- Decrease the concentration of zinc ions \([\text{Zn}^{2+}]\)
- Increase the concentration of copper ions \([\text{Cu}^{2+}]\)

5. **Conclusion:**
Therefore, to increase the EMF of the Daniel cell, we can:
- Decrease the concentration of zinc ions (Option D)
- Increase the concentration of copper ions (Option B)

Thus, the correct options to increase the EMF of the Daniel cell are **Option B (Increase concentration of Cu) and Option D (Decrease concentration of Zn)**.