Question

During electrolysis of brine, a gas ‘G’ is liberated at the anode. When this gas ‘G’ is passed through slaked lime, a compound ‘C’ is formed, which is used for disinfecting drinking water.

(ii) State the chemical equation involved.

Answer 1

Brine:-

• Brine is a very concentrated salt solution in water.
• In various applications, brine may refer to salt solutions with concentrations ranging from around 3.5 percent to roughly 26 percent.

Electrolysis of Brine solution:

• The electrolysis of brine solution, which is a solution of sodium chloride ($\mathrm{NaCl}$) and Water (${\mathrm{H}}_2\mathrm{O}$), is a large-scale method utilized in the production of chlorine from Water.
• Sodium hydroxide ($\mathrm{NaOH}$) and hydrogen (${\mathrm{H}}_2$) are the two most essential compounds produced during the electrolysis of brine solution.
• The chlorine (${\mathrm{Cl}}_2$) and sodium hydroxide created during the procedure must be separated before reacting and forming another chemical.
• The chemical reaction which occurs at the negative cathode electrode:
  $2{\mathrm{H}}^{+}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2\left(\mathrm{g}\right)\uparrow$
• Other equations for the reactions at the negative terminal:
  $2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}\to {\mathrm{H}}_2\left(\mathrm{g}\right)\uparrow +2{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)$
• The reactions which occur at the positive terminal i.e. anode are:
  ${\mathrm{Cl}}_2\left(\mathrm{aq}\right)\to 2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)+2{\mathrm{e}}^{-}$
• Other equations for the reactions at the positive terminal:
  ${\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)\to \mathrm{NaOH}\left(\mathrm{aq}\right)$
• When chlorine is passed through slaked lime, ${\mathrm{CaOCl}}_2$is formed as shown below:

$\underset{\mathrm{Slaked}\mathrm{lime}}{\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{l}\right)}+\underset{\mathrm{Chlorine}}{{\mathrm{Cl}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Calcium}\mathrm{hypochlorite}}{{\mathrm{CaOCl}}_2\left(\mathrm{l}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

Thus, the chemical reaction involved is the reaction between slaked lime and chlorine.