The number of moles of hydrogen molecules required to produce 20 moles of ammonia through Haber's process is

$$\begin{gathered} \text{ Haber's process, }{\mathrm{N}}_2+3{\mathrm{H}}_2\to 2{\mathrm{NH}}_3 \\ 2\text{ moles of }{\mathrm{NH}}_3\text{ are formed by }3\text{ moles of }{\mathrm{H}}_2\text{ . } \\ \therefore 20\text{ moles of }{\mathrm{NH}}_3\text{ will be formed by }30\text{ moles of }{\mathrm{H}}_2\text{ . } \end{gathered}$$