Chemistry - Mole Concept Question with Solution | TestHub

Number of moles$\text{=}\frac{\text{weight}\text{in}\text{gm}}{\text{atomic}\text{weight}}$
Number of moles Li$=\frac{7}{1000\times 7}=10^{-3}$
Number of moles of Na$=\frac{23}{1000\times 23}\times =10^{-3}$
Amount of energy = moles$\times$energy needed for 1 mole.
So, the amounts of energies required for$10^{-3}$mole each of Li and Na are 520 kJ$\times 10^{-3}$or 520 J and 495 J respectively.