Which one of the following reactions is not possible?

Options

A. `Ca+H_(2)SO_(4)toCaSO_(4)+H_(2)`
B. `Cu+H_(2)SO_(4)toCuSO_(4)+H_(2)`
C. `Zn+H_(2)SO_(4)toZnSO_(4)+H_(2)`
D. `Mg+H_(2)SO_(4)toMgSO_(4)+H_(2)`

Explanation

To determine which of the given reactions is not possible, we will analyze each reaction based on the reactivity of the metals involved. The key concept here is that a more reactive metal can displace a less reactive metal from a compound.

### Step-by-Step Solution:

1. **Identify the Metals and Their Reactivity**:
- The metals involved in the reactions are Calcium (Ca), Magnesium (Mg), Zinc (Zn), Copper (Cu), and Hydrogen (H).
- The order of reactivity from most reactive to least reactive is:
- Calcium (Ca) > Magnesium (Mg) > Zinc (Zn) > Hydrogen (H) > Copper (Cu)

2. **Analyze Each Reaction**:
- **Reaction 1**: Calcium displacing hydrogen from H2SO4.
- Since Calcium is more reactive than Hydrogen, this reaction is possible.
- **Reaction 2**: Copper displacing hydrogen from H2SO4.
- Copper is less reactive than Hydrogen, so it cannot displace hydrogen. This reaction is **not possible**.
- **Reaction 3**: Zinc displacing hydrogen from H2SO4.
- Zinc is more reactive than Hydrogen, so this reaction is possible.
- **Reaction 4**: Magnesium displacing hydrogen from H2SO4.
- Magnesium is more reactive than Hydrogen, so this reaction is possible.

3. **Conclusion**:
- The reaction that is not possible is the one where Copper attempts to displace Hydrogen from H2SO4.

### Final Answer:
The reaction that is not possible is the one where Copper displaces Hydrogen from H2SO4.