Redox reactions

Question

How many mL of 0.150 M solution (MnO4) - are needed to act without residue with 15 mL of 0.250 M solution of Fe2 + ions in acidic environment, if during the redox reaction Fe2 + is oxidized to Fe3 + and (MnO4) - reduced to Mn2 +.

Answer 1

Write the correctly balanced equation (if you need help doing this, post a separate question):

5Fe²⁺ + MnO₄^- + 8H⁺ ==> 5Fe³⁺ + Mn²⁺ + 4H₂O

moles Fe2+ present = 15 ml x 1 L/1000 ml x 0.250 mol/L = 0.00375 moles Fe2+

moles MnO₄^- required = 0.00375 mol Fe²⁺ x 1 mol MnO₄^- / 5 mol Fe²⁺ = 0.000750 mol MnO₄^- required

Volume MnO₄^- required: (x L)(0.150 mol/L) = 0.000750 mol

x = 0.00500 L = 5.00 mls of MnO₄^-