Question

How many oxygen atoms in a `300*g` mass of calcium carbonate?

Answer 1

We work out (i) the molar quantity of `CaCO_3`, and (ii) the constituent quantity of oxygen.

Explanation:

`"Moles of calcium carbonate, "(300*g)/(100.09*g*mol^-1)` `~=` `3*mol`.

Given the elemental makeup, in such a quantity there are `3` moles of calcium, `3` moles of carbon, and `9` moles of oxygen.

But what is a mole? It is simply a LARGE number that relates to a given mass of stuff. In `1` `mol` of stuff there are `6.022xx10^23` individual particles of that stuff.

So given 3 moles of calcium carbonate, there are 3 moles of calcium, 3 moles ofcarbon, and 9 moles of oxygen atoms.

So `"number of oxygen atoms"` `=` `9*molxxN_A`

`=` `6.022xx10^23*mol^-1xx9*mol" oxygen atoms"` `=` `"oxygen atoms"??`

What is the mass of this quantity of oxygen atoms, and how do you know?

See here for another examples of this process.