Question

On heating soda lime with sodium acetate a colorless gas ‘A ‘ is evolved. This gas is lighter than air. Name the gas ‘A’. The gas burns with a blue flame in excess of oxygen. Write the chemical equation for it.

Answer 1

• Soda lime is a mixture of Sodium hydroxide$\mathrm{\left(}\mathrm{NaOH}\mathrm{\right)}$ and Calcium oxide$\mathrm{\left(}\mathrm{CaO}\mathrm{\right)}$
• Sodium acetate$\mathrm{\left(}{\mathrm{CH}}_{\mathrm{3}}\mathrm{COONa}\mathrm{\right)}$ on heating with soda lime gives methane$\left({\mathrm{CH}}_4\right)$, a colorless gas 'A'.

$\underset{\mathrm{Sodium}\mathrm{acetate}}{{\mathrm{CH}}_3\mathrm{COONa}\left(\mathrm{aq}\right)}+\underset{\mathrm{Sodium}\mathrm{hydroxide}}{\mathrm{NaOH}\left(\mathrm{aq}\right)}\stackrel{\mathrm{CaO}/\mathrm{heating}}{\to }\underset{\mathrm{Methane}}{{\mathrm{CH}}_4\left(\mathrm{g}\right)}+\underset{\mathrm{Sodium}\mathrm{carbonate}}{{\mathrm{Na}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)}$

The color less gas ‘A’ is Methane.

• Methane is lighter than air.
• Methane is very good fuel and hence it burns with a blue flame in excess of oxygen.
• The balanced combustion equation of methane is as represented below :

$\underset{\mathrm{Methane}}{{\mathrm{CH}}_4\left(\mathrm{g}\right)}+\underset{\mathrm{Oxygen}}{2{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Carbon}\mathrm{dioixde}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Water}}{2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)}$