Question

How many moles does a `44*g` mass of carbon dioxide represent?

Answer 1

Well, a mass `44*g` mass of carbon dioxide clearly specifies `"ONE MOLE"` of carbon dioxide.

Explanation:

Why `"clearly"`, because we get the number of moles of stuff by using the quotient `"mass"/"molar mass"`.

Now the molar mass of `"carbon dioxide"` is `12.01*g*mol^-1+2xx15.999*g*mol^-1=44.0*g*mol^-1`. From where did I get the individual atomic molar masses?

And thus the quotient: `(44.0*g)/(44.0*g*mol^-1)=1*mol`.

Now look at the formula, each formula unit of `CO_2` is constituted by one carbon, AND TWO OXYGEN ATOMS. And therefore is we expand the quantities to moles, we SPECIFY PRECISELY `"2 moles of oxygen atoms............."`

This idea of equivalence, of the use of mass to specify the precise numbers of atoms and molecules that are present is central to the idea of stoichiometry. If you can master this idea, you won't have too much trouble with chemical calculations. Work at it, and a little bit of study will pay off. Good luck.