Haber’s process N2(g)+3H2(g)⇌2NH3(g)
According to the reaction,
2 moles of ammonia are produced from 3 moles of H2
i.e., 1 mole of ammonia is produced from 23 moles of H2
Thus, 20 moles of ammonia =23×20=30 moles of H2
Hence, 30 moles is the correct option.