Which of the following pairs will give displacement reaction? NaCl solution and copper metal, `MgCl_2` solution and aluminium metal, `FeSO_4` solution and silver metal, AgNO_3` solution and copper metal.

Options

A. NaCl solution and copper metal
B. `MgCl_2` solution and aluminium metal
C. `FeSO_4` solution and silver metal
D. `AgNO_3` solution and copper metal.

Explanation

To determine which pairs will give a displacement reaction, we need to refer to the reactivity series of metals. A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its compound.

### Step-by-Step Solution:

1. **Identify the Reactivity of Metals**:
- The reactivity series ranks metals from most reactive to least reactive. Commonly, the order is:
- Potassium (K)
- Sodium (Na)
- Calcium (Ca)
- Magnesium (Mg)
- Aluminum (Al)
- Zinc (Zn)
- Iron (Fe)
- Tin (Sn)
- Lead (Pb)
- Hydrogen (H)
- Copper (Cu)
- Silver (Ag)
- Gold (Au)

2. **Analyze Each Pair**:
- **Pair 1**: NaCl solution and copper metal
- Sodium (Na) is more reactive than copper (Cu). Therefore, copper cannot displace sodium from NaCl. **No reaction.**

- **Pair 2**: MgCl₂ solution and aluminum metal
- Magnesium (Mg) is more reactive than aluminum (Al). Therefore, aluminum cannot displace magnesium from MgCl₂. **No reaction.**

- **Pair 3**: FeSO₄ solution and silver metal
- Iron (Fe) is more reactive than silver (Ag). Therefore, silver cannot displace iron from FeSO₄. **No reaction.**

- **Pair 4**: AgNO₃ solution and copper metal
- Copper (Cu) is more reactive than silver (Ag). Therefore, copper can displace silver from AgNO₃, forming Cu(NO₃)₂ and releasing silver. **Reaction occurs.**

3. **Conclusion**:
- The only pair that will give a displacement reaction is **AgNO₃ solution and copper metal**.

### Final Answer:
The pair that will give a displacement reaction is **AgNO₃ solution and copper metal**.

---