What would likely occur if #"potassium iodide"# were added to #"ferric nitrate"#?

1 Answer
Mar 11, 2017

Answer:

#Fe(NO_3)_3(aq) + 3KI(aq) rightleftharpoons3K(NO_3)(aq) + FeI_3(aq)#

Explanation:

This is a type of metathesis reaction, i.e. a partner exchange reaction. Neither of the products are particularly insoluble, and they would remain in solution as the aquated ions, i.e. #Fe^(3+)#, #I^(-)# etc.

Additional redox reactions are conceivable, i.e. reduction of ferric to ferrous ion, or oxidation of iodide ion to tri-iodide, i.e. #I_3^-#:

#Fe^(3+) +e^(-) rarr Fe^(2+)# #E^(0)=0.77*V#

#I^(-) rarr 1/2I_2 + e^(-)# #E^(0)=-0.54*V#

#3I^(-) rarr I_3^(-) +2e^(-)# #E^(0)=??*V#

Oxidation of the iodide anion might indeed drive the ferric ion reduction. The #E^0# values show that the reaction is certainly thermodynamically feasible.

In the absence of further information, we invoke the given, so-called #"metathesis or partner-exchange reaction"#, which proceeds WITHOUT redox transfer.