Question

Give two examples of the following change occurring during a chemical reaction:

Evolution of a gas

Answer 1

Chemical reaction- A chemical reaction is the change of a substance into a new one that has a different chemical identity.

• Some chemical reactions are observed by the evolution of a gas.
• Two examples of it are given below.

Evolution of a gas-

• In the above example, electricity is passed through Sodium chloride solution, Sodium chloride decomposes into Sodium and, Chlorine gas is evolved.
• $\underset{\mathrm{Sodium}\mathrm{chloride}\mathrm{solution}}{2\mathrm{NaCl}\left(\mathrm{aq}\right)}\stackrel{\mathrm{electricity}}{\to }2\underset{\mathrm{Sodium}}{\mathrm{Na}\left(\mathrm{s}\right)}+\underset{\mathrm{Chlorine}}{{\mathrm{Cl}}_2\left(\mathrm{g}\right)}$
• When Zinc is placed in Sulphuric acid, Zinc is more reactive than Hydrogen displaces it from the acid, and forms zinc sulfate and hydrogen gas.
• $\underset{\mathrm{Zinc}}{\mathrm{Zn}\left(\mathrm{s}\right)}+\underset{\mathrm{Sulphuric}\mathrm{acid}}{{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)}\to \underset{\mathrm{Zinc}\mathrm{sulphate}}{{\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\uparrow }$