[medic2PA]

"A sample of calcium metal is contaminated by a certain amount of highly toxic, radioactive thorium methal (Th). A 10.00 gram sample of this mixture is dissolved in acid and reacted with excess sodium oxalate to form a precipitate which is a mixture of calcium oxalate, CaC2O4, and thorium oxalate, Th(C2O4)2. The total mass of this precipitate is 31.03g. Determine the mass of each metal in the original 10.00 g mixture.

Here's what i did:
let x= Ca, y= Th, x+y=10

xgCA * 1molCA/40.08gCa * 1mol CaC2O4/1mol Ca * 128.08g CaC2O4/1mol CaC2O4 = 3.196g XgCaC2O4

ygTh * 1molTh/232.04gTh * 1 mol Th(C2O4)2/ 1 mol Th * 408.04g Th(C2O4)2/ 1mol Th(C2O4)2= 1.758y g Th(C2O4)2

3.196x + 1.758y = 31.03

solve for x and y

I get y =47.38 and x = -37.67

they add up to 10 but are obviously wrong! I also tried the same set up as above but added the MW of CaC2O4 and Th(C2O4)2 together as the precipitate combined. But ended up getting numbers way off too. Am I missing a number of moles that doesnt equal one somewhere? what else can I try?

Thanks!

[Borek]

Check your math. Equations seem to be correct, solution is wrong.