Question

A metal 'M' on reacting with dilute acid liberates a gas 'G'. The same metal also liberates gas 'G' when reacts with a base.

1. Write the name of gas 'G'.
2. How will you test the presence of this gas?
3. Write chemical equations for the reactions of the metal with (1) an acid and (2) a base.

Answer 1

1. The gas G is hydrogen gas.
2. Bring a burning candle close to the hydrogen source to perform a typical test for hydrogen (H₂) gas. Hydrogen gas then burns with a squeaky pop sound. The 'pop' that hydrogen gas makes when it burns can be used to identify it. The 'pop' sounds like a tiny explosion.
3. Zinc metal reacts with both acid and base to produce hydrogen gas.
   $$\underset{\mathrm{Zinc}}{\mathrm{Zn}(\mathrm{s})}+\underset{\mathrm{hydroxide}}{\underset{\mathrm{sodium}}{2\mathrm{NaOH}(\mathrm{aq})}}\stackrel{\mathrm{Heat}}{\to }\underset{\mathrm{zincate}}{\underset{\mathrm{sodium}}{\mathrm{Na}{\phantom{A}}_2\mathrm{ZnO}{\phantom{A}}_2(\mathrm{aq})}}+\underset{\mathrm{Hydrogen}}{\mathrm{H}{\phantom{A}}_2(\mathrm{g})}\uparrow$$
   $$\mathrm{Zn}(\mathrm{s})+\underset{(\mathrm{dil}\text{.})}{\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}(\mathrm{aq})}}⟶\underset{\mathrm{Zinc}\mathrm{chloride}}{\mathrm{ZnCl}{\phantom{A}}_2(\mathrm{aq})}+\mathrm{H}{\phantom{A}}_2(\mathrm{g})\uparrow$$