Oxalic acid (H2C204), found in dark leafy green vegetables such as spinach, can

Question

Oxalic acid (H2C204), found in dark leafy green vegetables such as spinach, can inhibit iron absorption in the body. To determine the concentration of oxalic acid in a food, one can titrate a sample with a permanganate (Mn04") solution in the presence of sulfuric acid, which changes color on reaching the equivalence point. The balanded net lonic equation for this titration is given here. 5H2C2O4(aq) + 2 MnO4-(aq) + 6H30"(aq) 10 CO2(g) + 2 Mn2+(aq) + 14 H2O0 If one cup of spinach contains approximately 182 mg of oxalic acid, how many milliters of a 0.0100 M potassium permanganate solution would be required to reach the equivalence point? mL

Explanation / Answer

mass of oxalic acid = 182 mg = 0.182 g

moles of oxalic acid =0.182 / 90.035= 2.02 x 10^-3 mol

from the balanced equation :

5 mol H2C2O4 ---------------> 2 mol KMnO4

2.02 x 10^-3 mol   ----------------> ??

moles of KMnO4 = 2.02 x 10^-3 mol x 2 / 5 = 8.09 x 10^-4 mol

moles = Molarityx volume

8.09 x 10^-4 = 0.0100 x voolume

volume of KMnO4 = 80.9 mL

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