Question

What is Mohr titration?

Answer 1

1. Mohr titration is defined as the type of titration which helps in determining the Chloride ion $\left({\mathrm{Cl}}^{-}\right)$ concentration when it is titrated against Silver nitrate$\left({\mathrm{AgNO}}_3\right)$.
2. When we add Silver nitrate$\left({\mathrm{AgNO}}_3\right)$ to chloride solution it forms Silver Chloride$\left(\mathrm{AgCl}\right)$ precipitates.
   ${\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)\to \mathrm{AgCl}\left(\mathrm{s}\right)$
3. When all the Chloride ions are precipitated, the end point is reached.
4. Silver ions ${\left(\mathrm{Ag}\right)}^{+}$that are left in the solution will react with the Chromate ion ${\left({\mathrm{CrO}}_4\right)}^{2-}$of the indicator Potassium chromate$\left({\mathrm{K}}_2{\mathrm{CrO}}_4\right)$ to form a red-brown precipitate of Silver chromate $\left({\mathrm{Ag}}_2{\mathrm{CrO}}_4\right)$.
   $2{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{CrO}}_4^{2-}\left(\mathrm{aq}\right)\to {\mathrm{Ag}}_2{\mathrm{CrO}}_4\left(\mathrm{s}\right)$
5. So by this method Chloride ion concentration can be determined in any source like seawater, sewage, etc.