Solution: Manganese in an ore can be determined by treating the ore wi...

Question

Manganese in an ore can be determined by treating the ore with a measured, excess quantity of sodium oxalate (Na2C2O4) to reduce MnO2(s) to MnCl 2(aq) followed by determination of the unreacted sodium oxalate by titration with potassium permanganate. The equations for this two step process are:

MnO2(s) + Na2C2O4(aq) + 4HCl(aq) → 2MnCl 2(aq) + 2CO2(g) + 2H2O(l) +2NaCl(aq)

2KMnO4(aq) + 5Na2C2O4(aq) + 16HCl(aq) → 2MnCl 2(aq) + 10CO2(g) + 8H2O(l) + 10NaCl(aq)

If a sample is treated with 50.0 mL of 0.275 M Na 2C2O4(aq) and the unreacted Na 2C2O4(aq) requires 18.28 mL of 0.1232 M KMnO4(aq), calculate the number of grams of manganese in the sample. (NOTE: use the equations as written despite the fact they are not completely balanced)