Chemistry calculation problem. plzz help?

In this exercise, we are calculating the percentage of calcium carbonate in an impure sample. 0.607 g of the impure sample are reacted with excess dilute HCl. The calcium ions liberated are precipated as calcium ethanediote by adding excess aqueous ethanedioic acid. The precipitate is filtered and thoroughly washed with distilled water so as to remove all trace of ethanedioic acid. It is then completely dissolved in 100 cm^3 of 1 mol dm^-3 sulphuric acid. 25 cm^3 of the clear solution requires 28.50 cm^3 of 0.0200 mol dm^-3 KMNO4 for oxidising the C2O4^2- (I hope u understand what i mean here: the 2 is a subscript and the 4 also :)) ions to CO2. Write balanced equations for all reactions involved here, then perform the calculation.

Please help me with this problem. I would be really grateful. I just can't seem to work it out at all. The answer is 93.9%(i think thats the correct answer)

Answer:
The first reaction that occur is :
CaCO3 +2 HCl >> Ca2+ +2 Cl- + CO2 + H2O

Ca2+ + HOOCCOOH >> Ca(OOCCOO) (s) + 2H+

Moles H2SO4 used to dissolve calcium ethandiote =
100 x 1 / 1000 = 0.1 moles
Ca(OOCCOO) + 2H+ >>Ca2+ + HOOCCOOH

Moles KMnO4 = 28.50 x 0.0200 / 1000 = 0.00057
The balanced equation is :
2 MnO4- + 5 C2O42-+ 16H+ >>2 Mn2+ + 10CO2 + 8H2O

The ratio between MnO4- and C2O42- is 2 : 5
2 : 5 = 0.00057 : x
x = 0.00142 moles C2O42-

I hope this can help you
yes people let's do his entire homework for him
I know I cannot perform the calculation. Yet I may give you some insight as to helping yourself.
you say its an exercise in calculating. Usually this is done by moving figures around, writing it down and looking at it a different way. by your description/example, it seems anyone could be confused. I think if you would break down the paragraph into thinkable solutions, it might help you.
Do you know what I mean? Look at the end of the paragraph first, rewrite it, look in and through this paragraph. Is this a note you took down and forgot to write something? or is this straight from a teachers paper to you? Vivi

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