Question

Describe the preparation of hydrogen in the laboratory.

Answer 1

Laboratory preparation of Hydrogen

By the action of dilute acids on metals

• Metals like magnesium, zinc, and iron react with dilute hydrochloride acid and dilute sulphuric acid to form metal salts

$$\begin{gathered} \underset{\mathrm{Zinc}}{\mathrm{Zn}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{dil}\right)}\to \underset{\mathrm{Zinc}\mathrm{chloride}}{{\mathrm{ZnCl}}_2\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\uparrow \left(\mathrm{g}\right)} \\ \underset{\mathrm{Iron}}{\mathrm{Fe}\left(\mathrm{s}\right)}+\underset{\mathrm{Sulphuric}\mathrm{acid}}{{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{dil}\right)}\to \underset{\mathrm{Ferrous}\mathrm{sulphate}}{{\mathrm{FeSO}}_4\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\uparrow \left(\mathrm{g}\right)} \\ \underset{\mathrm{Iron}}{\mathrm{Fe}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{dil}\right)}\to \underset{\mathrm{Ferrous}\mathrm{chloride}}{{\mathrm{FeCl}}_2\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\uparrow \left(\mathrm{g}\right)} \end{gathered}$$

• The upward arrow indicates that hydrogen gas is released, which can be collected in a suitable apparatus
• All the metals are not equally reactive. some are more reactive than others.
• Alkali metals like sodium, potassium, alkaline earth metals like calcium, and metals like aluminum, zinc, and iron react to produce hydrogen.
• Out of all metals, zinc is used preferably due to its low cost, and purity of zinc granules. and more reactive metals often cause an explosive reaction
• On the other hand, metals like copper, mercury, silver, gold, and platinum do not produce hydrogen gas with acids
• The arrangement of the metal in a series in the descending order of reactivity is based on their reaction with a mineral acid. this is called the metal activity series.