Degenerate electron pressure will not be sufficient to prevent the core collapse of a white dwarf if its mass becomes $n$ times the solar mass. The value of $n$ is:

The binding energy per nucleon for a deuteron and an $\alpha$-particle are $x_1$ and $x_2$ respectively. The energy $Q$ released in the following reaction is:
$_1H^2 + _1H^2 \rightarrow {_2}{He}^4 + Q$

What is the fundamental reason for the chemical energy produced in a chemical process?

Draw conclusions from the two main features of the graph of binding energy per nucleon versus the atomic mass number $(A)$.

The mass of a proton is $1.0073 \; u$ and that of a neutron is $1.0087 \; u$ ($u =$ atomic mass unit). The binding energy of ${ }_2^4 \text{He}$ is (Given: helium nucleus mass $\approx 4.0015 \; u$):

The binding energy for the following nuclear reactions are expressed in $MeV$.
${ }_2 He ^3+{ }_0 n ^1 \rightarrow{ }_2 He ^4+20 \ MeV$
${ }_2 He ^4+{ }_0 n ^1 \rightarrow{ }_2 He ^5-0.9 \ MeV$
If $X_3, X_4, X_5$ denote the stability of ${ }_2 He ^3, { }_2 He ^4$ and ${ }_2 He ^5$,respectively,then the correct order is: