High School Chemisty Question

[buddy]

A sample of limestone (containing Calcium Carbonate, CaCo3) weighing 413 mg is treated with Oxalic Acid (H2C2O4), to give Calcium Oxalate (CaC2O4).

CaCO3 (S) + H2C2O4 (AQ) yields CaC2O4 (S) + H2O (L) + CO2 (G)

The mass of calcium oxalate is 472 mg.

What is the mass % of calcium carbonate in this limestone?

 

[Wilson]

Sorry Buddy..I cheated my way through high school chemistry.

 

[Bluemound Freak]

My Chemistry is a little rusty, but I beleive it is 78%!

You have to convert the amount of CACO3 into moles and then set up your equation with the known amounts and see how much yield you get of CAC2O4 then divide those numbers to get your percentage!

Correct me if I am wrong.

 

[DR STRANGELOVE]

General approach: Use mass of calcium oxalate and the balanced chemical equation to figure out the mass of CaCO3 present in the limestone. Take this value, divide by the total mass of limestone and multiply by 100

Step 1: Convert .472 g CaC2O4 into moles of CaC2)4
Step 2: Convert moles CaC2O4 into moles CaCO3 (1:1 ratio, so they're actually the same)
step 3: Convert moles CaCO3 into grams CaCO3
step 4: Take this mass, divide it by .413 g and multiply by 100

hope this helps,

 

[Bluemound Freak]

Does that not equal 78%?

 

[Bluemound Freak]

Nope it is 89%, I was converting the wrong way......

 

[KotysDad]

General approach: Use mass of calcium oxalate and the balanced chemical equation to figure out the mass of CaCO3 present in the limestone. Take this value, divide by the total mass of limestone and multiply by 100

Step 1: Convert .472 g CaC2O4 into moles of CaC2)4
Step 2: Convert moles CaC2O4 into moles CaCO3 (1:1 ratio, so they're actually the same)
step 3: Convert moles CaCO3 into grams CaCO3
step 4: Take this mass, divide it by .413 g and multiply by 100

hope this helps,

My turn to respond with this....

:look:

I avoided HS chemistry like the plague. Now I see why. :chairshot