A 31.0 mL solution of 0.155 M iron (III) perchlorate is prepared. This solution is then titrated with 27.1 mL of 0.250 M potassium hydroxide. What is the concentration of iron (III) perchlorate that remains in the solution?

Question

A 31.0 mL solution of 0.155 M iron (III) perchlorate is prepared. This solution is then titrated with 27.1 mL of 0.250 M potassium hydroxide. What is the concentration of iron (III) perchlorate that remains in the solution?

Answer 1

Fe(ClO4)3 + 3KOH ==> Fe(OH)3 + 3KClO4

millimols Fe(ClO4)3 = 31.0 x 0.155 =4.805
mmols KOH = 27.1 x 0.350 = 9.485

9.485 mol KOH x (1 mol Fe(ClO43)/3 mol KOH) = 9.485/3 = 3.162 mols Fe(ClO4)3.
So you should have 4.805-3.162 mmols Fe(ClO4) remaining unreacted. Check my arithmetic.