Question

1.) If 26.23 mL of potassium permanaganate solution is required to titrate 1.041 grams of ferrous ammonium sulfate hexahydrate, calculate the Molarity of the KMnO4 solution.

2.) If a 2.893 gram sample of an unknown containing iron requires 28.45 mL of the permanganate solution described in the previous question to reach the endpoint, calculate the percent iron in the unknown.

Answer 1

2KMnO4 + 10FeSO4 +8H2So4 -----------> K2SO4 + 2MnSO4 + 5Fe2(SO4)3 + 8H2O

2 moles      10 moles

no of moles of ferrous ammonium sulfate hexahydrate   = W/G.M.Wt

                                                                                           = 1.041/392   = 0.00265 moles

from balanced equation

10 moles of FeSo4 react with 2 moles of KMnO4

0.00265 moles of FeSO4 react with = 2*0.00265/10   = 0.00053 moles of KMnO4

no of moles of KMnO4   = molarity*volume in L

0.00053                         = molarity*0.02623

molarity                          = 0.00053/0.02623   = 0.02 M