Question

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

Change of colour

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 change of color of reactants.
• Two examples of it are given below.

Change of color-

• When red Lead oxide gets heated, yellow Lead monoxide is formed.
• $\underset{\mathrm{Lead}\mathrm{oxide}\left(\mathrm{red}\right)}{2{\mathrm{Pb}}_3{\mathrm{O}}_4\left(\mathrm{s}\right)}\stackrel{\mathrm{Heat}}{\to }\underset{\mathrm{Lead}\mathrm{monoxide}\left(\mathrm{yellow}\right)}{6\mathrm{PbO}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}$
• When a few pieces of Iron are added to the blue Copper sulfate solution, the color of the solution fades and turns into light green due to the formation of ferrous sulfate.
• $\underset{\mathrm{Iron}}{\mathrm{Fe}\left(\mathrm{s}\right)}+\underset{\mathrm{Copper}\mathrm{sulphate}}{{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)}\to \underset{\mathrm{Ferrous}\mathrm{sulphate}}{{\mathrm{FeSO}}_4\left(\mathrm{aq}\right)}+\underset{\mathrm{Copper}}{\mathrm{Cu}\left(\mathrm{s}\right)}$