Question

 

In this experiment, iron (III) (Fe3+) reacts with thiocyanate ion (SCN-) to form the deep red complex ion, FeSCN2+. The intensity of the red color will tell you if [FeSCN2+] changes.

You will make three changes to this equilibrium system:

• Adding solid ammonium thiocyanate (NH4SCN). NH4SCN is a soluble solid which will dissociate in water to form NH4+ ions and SCN- ions.
• Adding silver nitrate (AgNO3) which removes SCN- ions from the equilibrium system by forming an insoluble white precipitate.
• Heating and cooling the system.

Find the Reaction Equation:

Answer 1

From solid ammonium thiocyanate (NH₄SCN)

NH$_4^+$ and SCN$^-$ ions

Reaction :

Fe³⁺ ( from equilibrium) + SCN$^-$ (from NH₄CN) $\to$ FeSCN²⁺

From silver nitrate AgNO₃

Ag²⁺ and NO$_3^{2-}$

Reaction:

Fe³⁺ (from equilibrium) + NO$_3^{2-}$ (from AgNO₃) $\to$ FeNO$_3^+$ (Insoluble white precipitate)