Chapter U6.5, Problem 1E

Interpretation Introduction

Interpretation: The reason of different colours of different solution consisting of ${\text{Fe}}^{\text{3+}}$ , ${\text{SCN}}^{-}$ and ${\text{FeSCN}}^{2+}$ ions needs to be explained.

Concept Introduction: According to Le Chatelier’s principle if an equilibrium is shifted to a stress, the equilibrium shift in such a way as to reduce the stress.

Answer to Problem 1E

The colour changes according to Le Chatelier’s principle.

Explanation of Solution

The colour changes arises according to Le Chatelier’s principle in different solution consisting of ${\text{Fe}}^{\text{3+}}$ , ${\text{SCN}}^{-}$ and ${\text{FeSCN}}^{2+}$ . Addition of more ${\text{Fe}}^{\text{3+}}$ ions has result increase the concentration of complex ferri-sulphocyanide ion. If some sulphocyanide salt is added to the solution, the colour will become more darken due to the formation of ferri-sulphocuanide ion.

Conclusion

In a chemical equilibrium increasing the concentration of the reactants results in shifting the equilibrium in favour of the products and increasing the concentration of products results in shifting of equilibrium in favour of the reactant.