$$ \mathrm{N}_{2(\mathrm{~g})}+3 \mathrm{H}_{2(\mathrm{~g})} \rightleftharpoons 2 \mathrm{NH}_{3(\mathrm{~g})} $$

$$20 \mathrm{~g} \quad ~~~5 \mathrm{~g}$$

Consider the above reaction, the limiting reagent of the reaction and number of moles of $$\mathrm{NH}_{3}$$ formed respectively are :

The first ionization enthalpy of Na, Mg and Si, respectively, are : 496, 737 and $$786 \mathrm{~kJ} \mathrm{~mol}^{-1}$$. The first ionization enthalpy ($$\mathrm{kJ} \,\mathrm{mol}^{-1}$$) of $$\mathrm{Al}$$ is :

The reaction of zinc with excess of aqueous alkali, evolves hydrogen gas and gives :

Number of lone pairs of electrons in the central atom of $$\mathrm{SCl}_{2}, \mathrm{O}_{3}, \mathrm{ClF}_{3}$$ and $$\mathrm{SF}_{6}$$, respectively, are :