Iron displaces copper from copper sulphate solution, zinc displaces iron from ferrous sulphate solution and copper displaces silver from silver nitrate solution. Write the reactions involved and arrange the four metals involved in order of their reactivity.

Write balanced chemical equations for the following reaction:

$\mathrm{M}\mathrm{n}{\mathrm{O}}_2\left(\mathrm{s}\right)+\underset{\mathrm{C}\mathrm{o}\mathrm{n}\mathrm{c}.}{\mathrm{H}\mathrm{C}\mathrm{l}\left(\mathrm{a}\mathrm{q}\right)}\stackrel{\mathrm{H}\mathrm{e}\mathrm{a}\mathrm{t}}{\to }\mathrm{M}\mathrm{n}\mathrm{C}{\mathrm{l}}_2\left(\mathrm{s}\right)+\mathrm{C}{\mathrm{l}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\mathrm{}$

Write balanced chemical equations for the following reaction:

$\mathrm{Z}\mathrm{n}\left(\mathrm{s}\right)+\mathrm{H}\mathrm{C}\mathrm{l}\left(\mathrm{a}\mathrm{q}\right)\to \mathrm{Z}\mathrm{n}\mathrm{C}{\mathrm{l}}_2\left(\mathrm{a}\mathrm{q}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

We have often noticed that a food containing oil or fat, if left for a long time i.e. stale food, develops a bad taste and bad smell. This is because the oils and fats in such foods get oxidised with the passage of time. The oxidation of oils or fats result into a bad smell and bad taste.
Read the above passage and answer the following question:

State any two methods to prevent rancidity.

We have often noticed that a food containing oil or fat, if left for a long time i.e. stale food, develops a bad taste and bad smell. This is because the oils and fats in such foods get oxidised with the passage of time. The oxidation of oils or fats result into a bad smell and bad taste
Read the above passage and answer the following question:

Which method can be followed at home for the preservation of food ?