Chapter 21, Problem 46R

To determine

The effect of dissolving an ionic compound Copper sulfate in water.

Answer to Problem 46R

When pure copper sulfate is added in water, it starts dissolving. As a result, water molecules begin to come between ${\mathrm{Cu}}^{2+}$ and ${\mathrm{SO}}_4^{2-}$ ions since the ionic force of attraction between the cation ( ${\mathrm{Cu}}^{2+}$ ) and anion ( ${\mathrm{SO}}_4^{2-}$ ) gets eventually weaker with time and the two ions get separated.

  ${\mathrm{CuSO}}_4+6H_{2}O\to {\left[Cu{\left(H_{2}O\right)}_6\right]}^{2+}+S{O}_4{}^{2-}$

The reaction is used as a test for water. The white solid turns blue in the presence of water.

Explanation of Solution

Introduction:

When an ionic compound is added in water and stirred, it is dissociated to form ions.

When pure copper sulfate is added in water, it dissolveswith release of small amount of heat. The water molecules break the attractions between ${\mathrm{Cu}}^{2+}$ and ${\mathrm{SO}}_4^{2-}$ .

  ${\mathrm{CuSO}}_4+6H_{2}O\to {\left[Cu{\left(H_{2}O\right)}_6\right]}^{2+}+S{O}_4{}^{2-}$

When copper sulphate is dissolved in water, the color of solution changes from colorless to blue. Due to this colour it is known as “Blue Vitriol”.

Conclusion:

Thus,when pure copper sulfate is dissolved in water, a blue color solution is formed.