Solutions of potassium can also be standardized using Mohr\'s salt, Fe(NH4)2(SO4

Question

Solutions of potassium can also be standardized using Mohr's salt, Fe(NH4)2(SO4)2*6H2O. The reaction equation is:

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

A sample of Fe(NH4)2(SO4)2*6H2O weighing 0.9584 grams was dissolved in 70 mL deionized water and 10mL of 3M sulfuric acid, H2SO4, was added. The solutions was titrated at room temp with potassium permanganate solution, KMnO4: 35.68 mL of solution was required to completely react with the Fe2+ ion. Use this data to determine the concentration of the KMnO4 solution.

Explanation / Answer

Ans.)

2KMnO4 + 5Na2C2O4 + 8H2SO4 ----> 2MnSO4 + K2SO4 + 5Na2SO4 + 10CO2 + 8H2O

Molar mass (molecular weight) of Na2C2O4 is 133.99 g/mol
Molar mass (molecular weight) of KMnO4 is 158.03 g/mol

According to the reaction 2mol KMnO4 reacts with 5mol Na2C2O4

0.100gNa2C2O4 * 1molNa2C2O4/133.99gNa2C2O4 * 2molKMnO4/5molNa2C2O4 * 1/0.025LKMnO4 = 0.0119M KMnO4

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