Hydrogen cannot be prepared by the action of dil. $H _{2} SO _{4}$ on copper or mercury as these two metals cannot displace hydrogen from acids. Action of dil. $H _{2} SO _{4}$ on $Pb$ stops after some time due to the formation of insoluble $PbSO _{4}$. Only iron reacts rapidly with dil. $H _{2} SO _{4}$ to give $H _{2}$.
Laboratory Preparation of Dihydrogen is given below:
Reacting Zinc with Acid - One common way to produce or prepare dihydrogen gas in the lab is by reacting Zinc with a diluted acid.
\(Zn + H_2SO_4 → ZnSO_4 + H_2\)
\(Zn +HCl → ZnCl_2 + H_2\)
Reacting Zinc with Alkaline - Zinc can also react with an aqueous alkali such as Sodium Hydroxide, The sodium and zinc will combine and produces dihydrogen as another product. The reaction is given as:
\(Zn + 2NaOH → Na_2ZnO_2 + H_2\)
Commercial Preparation of Dihydrogen - The commercial preparation of hydrogen is a huge industry due to the high demand for hydrogen in the production of fertilizers and the oil-refining process.