Question

Assertion: Thermonuclear fusion reactions may become the source of unlimited power for mankind.
Reason: A single fusion event involving isotopes of hydrogen produces more energy than energy from nuclear fission of ${}_{93}^{235}U$.
A. Both assertion and reason are correct and reason is the correct explanation for assertion
B. Both assertion and reason are correct but reason is not the correct explanation for assertion.
C. Assertion is correct but reason is incorrect
D. Both assertion and reason are incorrect

Answer 1

Hint-In a thermonuclear fusion reaction two small nuclei combine together at a very high temperature to form another large nucleus. Thermonuclear fusion produces a clean source of energy.
In a fission reaction one large nucleus splits into daughter nuclei. In the nuclear fission of ${}_{93}^{235}U$ much more energy is released than that produced in a single fusion reaction involving isotopes of hydrogen.

Step by step solution:
In a thermonuclear fusion reaction two small nuclei combine together at a very high temperature to form another large nucleus. It takes place only at high temperature in order to overcome the electrostatic repulsion between the combining nuclei. The high temperature provides enough kinetic energy to the particles to overcome the coulomb repulsion
Whereas in a fission reaction one large nucleus splits into daughter nuclei. In the nuclear fission of ${}_{93}^{235}U$ much more energy is released than that produced in a single fusion reaction involving isotopes of hydrogen.
Thermonuclear fusion produces a clean source of energy. It is true that it may become the source of unlimited power for mankind. So, the assertion given is correct. But since energy produced during fusion of isotopes of hydrogen produces energy less than that produced in a nuclear fission of ${}_{93}^{235}U$.
The reason given is incorrect.

Therefore, the correct answer is option C.

Note: Nuclear fission occurs only at high temperature because the particle needs enough kinetic energy to overcome the coulomb repulsion between the two nuclei. But the nuclear fission reaction where the nucleus splits into small daughter nuclei can occur even at normal temperature.