A solution of sodium oxalate is used to standardize the normality of a potassium

Question

A solution of sodium oxalate is used to standardize the normality of a potassium permanganate solution. Each mol of sodium oxalate that reacts produces 2 equivalents of electrons. Each mole of potassium permanganate that reacts requires 5 equivalents of electrons. Normality (in redox reactions) is the number of equivalents of electrons per liter of solution. 1.008 grams of sodium oxalate (Na2C2O4) are completely dissolved in a 100.0 ml volumetric flask. 25.0 ml of the oxalate solution ar titrated to the endpoint with 15.6 ml of the permanganate solution. What is the Normality and Molarity of the potassium permanganate solution?

Explanation / Answer

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

moles of Na2C2O4 = 1.008 / 134 = 7.52 x 10^-3 mol

Molarity of Na2C2O4 = 7.52 x 10^-3 / 0.1 = 0.0752 M

moles of Na2C2O4 = 0.0752 x 25 / 1000 = 1.88 x 10^-3

from the balanced equation :

5 mol Na2C2O4   --------------> 2 mol KMnO4

1.88 x 10^-3 mol Na2C2O4   -------------> ??

moles of KMnO4 = 7.52 x 10^-4

Molarity = moles / volume = 7.52 x 10^-4 / 0.0156

Molarity of KMnO4 = 0.0482 M

Noramality = 0.0482 x 5

Noramality = 0.241 N

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