Oxalic acid (H2C204), found in dark leafy green vegetables such as spinach, can
ID: 551422 • Letter: O
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? mLExplanation / 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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