Question

The following questions deal with reactions involving the iron (III) nitrate solution.

A) Considering the pH of this solution, what two species, besides the Fe(H2O)6^3+ and NO3- ions and water, are present in a significant concentration?

B) write the equation for the reaction of a Ne (NO3)^3 solution with aqueous HNO3.

C) wirte the equation for the reaction of Fe(H2O)6^3+ with HCL solution.

D) write the equation for the reaction of SCN- with the complex ion produced in (c).

Answer 1

A) as given, when pH is involved there are definitely H+ Ions(also known as H3O+) and OH- ions.

B)  oxidation: Fe(NO3)2 with Fe's at +2, losing 1 electron ---> forming Fe(NO3)3 with Fe's at +3
reduction: HNO3 with N's at +5, takes 3 electrons -> forming NO with N's at +2

electrons balance as:
3 Fe(NO3)2 loses 3 e- ---> 3 Fe(NO3)3
1 HNO3 takes 3 e- -> 1 NO

which gives us:
3 Fe(NO3)2 + 1 HNO3 -> 3 Fe(NO3)3 +1 NO + H2O

to get the extra nitrates to make Fe(NO3)3 we add 3 additional HNO3 's that do not redox:
3 Fe(NO3)2 + 1 HNO3 & 3 HNO3 -> 3 Fe(NO3)3 +1 NO + H2O

balance H's:
3 Fe(NO3)2 + 1 HNO3 & 3 HNO3 -> 3 Fe(NO3)3 +1 NO + 2H2O

done, oxygens balance already...
just combine the two batches of HNO3 's:
3 Fe(NO3)2 & 4 HNO3 -> 3 Fe(NO3)3 +1 NO + 2H2O.

C) Fe(H2O)6 3+ with HCl solution
[Fe(H2O)6]3+ + 4HCl(aq)<==> [FeCl4]- + 4H+ + 6H2O

D)  SCN- with the complex ion produced in C
[FeCl4]- + SCN- <==> [FeSCN]2+ + 4Cl- .