# Calculating mass of oxygen in CaCO3...

1. Nov 9, 2015

### Sace Ver

1. The problem statement, all variables and given/known data
What would be the mass of oxygen in 2.5 x 102 g in CaCO3?
Given:
Mass 2.5 x 102
Molar Mass of CaCO3 which is 100.09 g/mol.

2. Relevant equations
mo=molar mass x number of o

3. The attempt at a solution
mo=100.09 g/mol x 3
mo=300.27 g of oxygen

Can someone tell me if I got this right? Thank you.

Last edited by a moderator: Nov 9, 2015
2. Nov 9, 2015

### SteamKing

Staff Emeritus
If you start with 250 g of CaCO3, how can you have 300.27 g of oxygen?

3. Nov 9, 2015

### SteamKing

Staff Emeritus
Here, you are assuming that all 100 g/mol is oxygen, which it is clearly not.

You need to figure out how many moles of CaCO3 there are in 250 g of the substance.

4. Nov 10, 2015

### Staff: Mentor

Assuming one mole of CaCO3 - how many moles of O (atomic oxygen)?

5. Nov 10, 2015

### Sace Ver

And then divide by 3 bc there is 3 atoms of oxygen?

6. Nov 10, 2015

### SteamKing

Staff Emeritus
There will be 3 moles of oxygen atoms in each mole of CaCO3.

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