Chem question help please!!?

Posted on 2016-04-09 14:44:00 in Chemistry by MARTEEN

Oxalic acid (H2C2O4) reacts readily with strong oxidants such as acidified potassium permanganate in a 
highly exothermic (heat producing) reaction according to the equation: 

2MnO4–(aq) + 5H2C2O4(aq) + 6H+(aq) → 2Mn2+(aq) + 8H2O(l) + 10CO2(g) 

An impure sample of oxalic acid of mass 7.18 g is dissolved in approximately 40 mL of deionised water in a volumetric flask and is then made up to 250.0 mL. A 20.00 mL aliquot of this solution is then titrated against a 0.100 M freshly prepared acidified potassium permanganate solution. The endpoint was reached when 17.9 mL of MnO4– (aq) had been added and the solution retained a permanent pink colour. 

a. Write the partial redox equation that represents the oxidation process in this reaction. 

b. Calculate the amount (in mol) of MnO4–(aq) required to reach the endpoint. 

c. Determine the amount (in mol) of oxalic acid in the aliquot. 

d. Determine the mass of pure oxalic acid in the original sample 

e. Hence determine the percentage of pure oxalic acid in the sample. 

f. State one source of error that could affect the accuracy of this determination.

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