[fanatic520]

Hi can someone please show me how to do this question? Thankss so much!

A mixture of CaCO3 and CaO weighing 0.722 g was heated to produce CO2. After heating, only CaO solid remains and it weighs 0.451 g.

Assuming all the CaCO3 decomposed to CaO and CO2, calculate the mass percent of CaCO3 in the original mixture.
(Express your answer to 1 decimal place.)

[Xilenir]

Not sure if this is too late to help anymore, but this is how I think (been a while since I took Intro Gen Chem though) the question should be solved.


First you should you should calculate how many moles of CaO there present after the rxn goes to completion

Based on that number of moles (8.042mmol) you can set up a system of equations to find out how much of that CaO from there initailly (14.64%) and how much CaO (85.36%) resulted from CaCO3 decomposition.

Those values will be your starting percentages.





http://i226.photobucket.com/albums/dd166/a...Stoich_0001.jpg

http://i226.photobucket.com/albums/dd166/a...Stoich_0002.jpg