# Homework Help: Calculating moles of CaCO3

1. Nov 15, 2015

### Sace Ver

1. The problem statement, all variables and given/known data
In 0.50 moles of CaCO3 how many moles of carbon are present? How many moles of oxygen are present?

Given:
0.50 moles of CaCO3
Molar mass is 100.9 g/mol

2. Relevant equations
n=m/M

3. The attempt at a solution

I'm not quite sure how to do this question would I begin by finding the mass?

Because if so the mass of CaCO3 would be 50.45 g I'm assuming because m=nM.

But then I do not know where to go from there would I find the mass of each of them?

2. Nov 15, 2015

### SteamKing

Staff Emeritus
You don't need to know the mass of CaCO3 to figure out how many moles of each constituent there are. You just need to know how many moles of CaCO3 you start with.

Look at it this way. How many molecules of a substance are in one mole of that substance?

If you know there is one atom of element X in each molecule, how many moles of X will there be for each mole of the substance?

3. Nov 15, 2015

### Sace Ver

1 molecule of substance is in one mole of a substance?

There will be 1 mole of C and 3 moles of O ?

4. Nov 15, 2015

### SteamKing

Staff Emeritus
You need to review the definition of mole:

https://en.wikipedia.org/wiki/Mole_(unit)

Yes, but not because you think there is one molecule in one mole.

5. Nov 15, 2015

### Sace Ver

6. Nov 15, 2015

### SteamKing

Staff Emeritus
No, but you still need to understand the concept of what a mole is.

A mole is a standard number of molecules of a substance. Think of it as being analogous to what a dozen is. It doesn't matter what we are talking about, be it a dozen doughnuts, or a dozen cars, or a dozen dogs, a dozen means twelve somethings.

Same thing with moles. One mole of a substance contains a standard number of somethings, in this case that number is waaaay more than 12. It is, in fact Avogadro's number of molecules in one mole of a substance.

Now, if one molecule of CaCO3 contains one Calcium atom, one Carbon atom, and three Oxygen atoms, then if we collected a dozen molecules of CaCO3, how many Calcium atoms, Carbon atoms, and Oxygen atoms would we have?
If we collected 10,000 molecules?
One million molecules?

Does the ratio of Calcium atoms to Carbon atoms to Oxygen atoms change depending on how many molecules of one substance are collected?

7. Nov 15, 2015

### Sace Ver

The ratio doesn't change, right?

8. Nov 15, 2015

### SteamKing

Staff Emeritus
Right.

9. Nov 20, 2015

### Sace Ver

Okay I tried this question once again.
Would I first find the number of carbon and oxygen and then find the mole?

10. Nov 20, 2015

### Sace Ver

The answer would be 0.5 mol of carbon and 1.5 mol of oxygen??? Would that be correct?

11. Nov 20, 2015

### SteamKing

Staff Emeritus
Yes.