If an electron and a positron annihilate,then the energy released is

What does the binding energy per nucleon show?

$A$ nuclide $1$ is said to be the mirror isobar of nuclide $2$ if $Z_1 = N_2$ and $Z_2 = N_1$. $(a)$ What nuclide is a mirror isobar of $_{11}^{23}Na$? $(b)$ Which nuclide out of the two mirror isobars has greater binding energy and why?

The binding energy per nucleon of ${ }_{8}^{16}O$ is $7.97 \text{ MeV}$ and that of ${ }_{8}^{17}O$ is $7.75 \text{ MeV}$. The energy required to remove one neutron from ${ }_{8}^{17}O$ is $\qquad \text{ MeV}$.

If the binding energy per nucleon for $_3{Li}^7$ and $_2{He}^4$ nuclei are $5.60 \, MeV$ and $7.06 \, MeV$ respectively,then the energy released in the reaction $_3{Li}^7 + _1H^1 \rightarrow 2 \, _2{He}^4$ is ...... $MeV$.

The energy equivalent to a substance of mass $1 \,g$ is