[j22rober]

How did I determine the amount of calcium carbonate when the only information that I have it contains 100mg of calcium. I know it is supposed to by 295mg calcium carbonate. Can any one work this out for me....

[Arkcon]

What else coes calcium carbonate contain besides calcium?  And how much "other things" per calcium does it contain?  And what do they "weigh"?  If you can answer these questions, you should be able to solve this problem.  Try some of the steps and lets see what you get.

[j22rober]

This is all the information that I have. I calculated the following:

CaCO3 --> Ca  + CO3

I have m= 100mg for Ca and MW of Ca= 40.08g/mol

Thus n = m/MW = [0.100g/(40.08g/mol)]  =0.002495mol of Ca

Since it is a 1:1 molar ratio I have that same amount of CaCO3

MW = 100.08 for CaCO3

Then m=n*MW = (0.002495mol)(100.08g/mol)(1000mg/g) = 249.7mg

However, I have been told the answer is 295mg.

This is not for school this is for work. I was given the answer by a senior colleague, who refuses to explain it. Can anyone tell me what I am doing wrong.

Thanks

[Borek]

250 mg is a correct answer when you are calculating mass of calcium carbonate CaCO₃. 295 mg would be correct for calcium carbonate monohydrate CaCO₃·H₂O.