stoichiometry!!! again.. =/?

Question

calcium oxide can be prepared by heatin calcium oxygen. How much calcium would be needed to make 15.0g of calcium oxide in this way??

is this da equation? : CaO --> Ca + O

and if its not wat is it?
and how do i solve this??

Answer 1

First, you need to have a proper balanced equation. You have the sequence reversed and oxygen gas is always O2, not O.

So 2Ca + O2 == 2CaO is where you start.

Divide the 15.0 g of CaO by its molecular mass (add up the parts) to get moles of CaO.

Now multiply by the correct molar ratio of 2/2 and it is the same moles of Ca.

Multiply by the molecular mass of Ca and you are done.

Answer 2

10.7g Ca

2 Ca + O2 --> 2 CaO

2:2 ratio of Ca:CaO, which is the same as 1:1

molar masses:
Ca: 40.08g/mol
CaO: 56.08g/mol

first convert 15.0g g CaO to moles and then multiply by molar mass of Ca. I like factor label.

15.0g CaO x 1mol CaO/56.0g CaO x 1mol Ca/1mol CaO x 40.08g Ca/1mol Ca = 10.7g Ca