Question

Choose the correct statement regarding the reaction given below:

${\text{Fe(NO}}_3{)}_3\text{(aq)}+3\text{KCNS (aq)}\leftrightharpoons {\text{Fe(CNS)}}_3\text{(aq)}+3{\text{KNO}}_3\text{(aq)}$

• A. The given reaction is irreversible in nature.
• B. The given reaction is reversible in nature.
• C. The red colour of the product is due to potassium nitrate.
• D. Formation of ferric thiocyanate takes place in two stages.

Answer 1

The correct option is B The given reaction is reversible in nature.

The given reaction is a reversible reaction for the formation of ferric thiocyanate and potassium nitrate from ferric nitrate and potassium thiocyanate. The red colour of the product is due to the formation of ferric thiocyanate. It formed in three stages:

(i) ${\text{Fe}}^{3+}+{\text{CNS}}^{-}\leftrightharpoons {\text{Fe(CNS)}}^{2+}$
(ii) ${\text{Fe(CNS)}}^{2+}{\text{CNS}}^{-}\leftrightharpoons {\text{Fe(CNS)}}_2^{+}$
(iii) ${\text{Fe(CNS)}}_2^{+}+{\text{CNS}}^{-}\leftrightharpoons {\text{Fe(CNS)}}_3$