In nuclear reactions which of the following conservation laws is not obeyed?

Options

A. conservation of mass
B. conservation of linear momentum
C. conservation of charge
D. conservation of total number of nucleons

Answer

To solve the question regarding which conservation law is not obeyed in nuclear reactions, we can analyze the different conservation laws one by one.

### Step-by-Step Solution:

1. **Understanding Conservation Laws**:
- In physics, conservation laws state that certain properties of isolated physical systems remain constant over time. The most relevant conservation laws in nuclear reactions include conservation of mass, conservation of energy, conservation of linear momentum, conservation of charge, and conservation of nucleons.

2. **Conservation of Mass**:
- In classical physics, mass is considered to be conserved in reactions. However, in nuclear reactions, a phenomenon known as mass defect occurs. This means that some mass is converted into energy according to Einstein's equation \(E=mc^2\). Therefore, the total mass before the reaction is not equal to the total mass after the reaction. Thus, conservation of mass does not hold in nuclear reactions.

3. **Conservation of Energy**:
- Although mass is not conserved, energy is conserved in nuclear reactions. The energy released during the reaction is equivalent to the mass defect. Therefore, the total energy (including the energy equivalent of mass) remains constant.

4. **Conservation of Linear Momentum**:
- Linear momentum is conserved in nuclear reactions. Even though mass is converted to energy, the momentum of the system remains constant. The particles produced in the reaction carry momentum that balances the initial momentum.

5. **Conservation of Charge**:
- Charge is conserved in nuclear reactions. The total charge before and after the reaction remains the same, as charge cannot be created or destroyed.

6. **Conservation of Nucleons**:
- The total number of nucleons (protons and neutrons) is also conserved in nuclear reactions. While individual nucleons may be transformed or rearranged, the total count remains the same.

### Conclusion:
From the analysis above, we can conclude that the conservation law that is not obeyed in nuclear reactions is the **Conservation of Mass**.

### Final Answer:
The correct option is **A: Conservation of Mass** does not apply to nuclear reactions.

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