When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of a :

Which of the following oxide(s) is/are soluble in water to form alkalies?

$\left(\mathrm{i}\right) {\mathrm{Na}}_2\mathrm{O}$                $\left(\mathrm{ii}\right) {\mathrm{SO}}_2$              $\left(\mathrm{iii}\right) {\mathrm{K}}_2\mathrm{O}$          $\left(\mathrm{iv}\right) {\mathrm{NO}}_2$

Study the diagram given below and identify the gas formed in the reaction.

${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{aq}\right)+6{\mathrm{O}}_2\left(\mathrm{aq}\right)\to 6{\mathrm{CO}}_2\left(\mathrm{aq}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

The above reaction is a/an example of 

Which of the following statements about the reaction given below are correct?

${\mathrm{MnO}}_2+4\mathrm{HCl}\to {\mathrm{MnCl}}_2+2{\mathrm{H}}_2\mathrm{O}+{\mathrm{Cl}}_2$

(i) $\mathrm{HCl}$ is oxidised to ${\mathrm{Cl}}_2$

(ii) ${\mathrm{MnO}}_2$ is reduced to ${\mathrm{MnCl}}_2$

(iii) ${\mathrm{MnCl}}_2$ acts as an oxidising agent

(iv) $\mathrm{HCl}$ acts as an oxidising agent