reducing property of some acids....help pls....?

Question

1.why does the formic acid with dilute sulfuric acid decolorized after having 3 drops of KMnO4?
2. why does oxalic acid with dilute sulfuric acid decolorized after having 1 drop of KMnO4?
3. why is the decolorization ocuured faster in oxalic acid than formic acid?
pls help me..... i need it badly...

Answer 1

Look at the half equations:

HCOOH ------> CO2 + 2H+ + 2e- and

(COOH)2 ------> 2CO2 + 2e- + 2H+

They both react with exactly the same numb er of moles of oxidising agent (acidified KMnO4), so you must check to see wther the concentrations of the two organic acid solutions was the same.

The solutions go colourless because the purple (MnO4)- ion is reduced to Mn2+:

(MnO4)- + 8H+ + 5e- ----> Mn2+ + 4H2O.