Question

Iron pyrite is dissolved in aqua regia and the iron in the solution is reduced to Fe²⁺. The solid sample is next dissolved in HCl and diluted to 100.0 mL. It is then titrated with a KMnO4 solution (molarity: .0201364558). Calculate the molarity of the Fe^2+ solution.

Balanced Equation: 5Fe²⁺ + 8H⁺ +MnO₄^- --> 4H₂O + Mn²⁺ + 5Fe³⁺

data:

Volume of Fe2+ solution (mL)	Volume of KMnO4 solution (mL)
15.0	14.5
20.0	19.5
25.0	24.5

Answer 1

Balanced Equation: 5Fe²⁺ + 8H⁺ +MnO₄^- --> 4H₂O + Mn²⁺ + 5Fe³⁺

Given that; KMnO4 solution (molarity: 0.0201364558)

For 1^st solution:

Volume of Fe2+ = 15.0 ml or 0.015 L

Volume of KMnO4 = 14.5 ml or 0.0145 L

First calculate the mole of MnO4- as follows:

Number of moles = molarity * volume in L

=0.0201 * 0.0145

= 0.0003 Mole MnO4-

Then mole of Fe2+;

0.0003 Mole MnO4- * 5 mole Fe2+ /1 Mole MnO4- =0.0015 mole Fe2+

Molrity = number of moles / volume In L

= 0.0015 mole Fe2+ /0.015

= 0.1 M

For 2 nd solution:

Volume of Fe2+ = 20.0 ml or 0.020 L

Volume of KMnO4 = 19.5 ml or 0.0195 L

First calculate the mole of MnO4- as follows:

Number of moles = molarity * volume in L

=0.0201 * 0.020

= 0.0004 Mole MnO4-

Then mole of Fe2+;

0.0004 Mole MnO4- * 5 mole Fe2+ /1 Mole MnO4- =0.002 mole Fe2+

Molrity = number of moles / volume In L

= 0.002 mole Fe2+ /0.020

= 0.1 M

For 3^rd solution:

Volume of Fe2+ = 25.0 ml or 0.025 L

Volume of KMnO4 = 14.5 ml or 0.0145 L

First calculate the mole of MnO4- as follows:

Number of moles = molarity * volume in L

=0.0201 * 0.0245

= 0.0005 Mole MnO4-

Then mole of Fe2+;

0.0005 Mole MnO4- * 5 mole Fe2+ /1 Mole MnO4- =0.002 5mole Fe2+

Molrity = number of moles / volume In L

= 0.0025 mole Fe2+ /0.025

= 0.1 M