# How do you calculate the number of grams in 0.865 moles?

Sep 20, 2016

As written I can you tell you how many particles there are in $0.865$ moles, but NOT the number of grams.

#### Explanation:

The mole is a collective number like a dozen, or a gross, or a score, etc. Admittedly it is a very large collective number.

If I have a mole of stuff, I have $6.022 \times {10}^{23}$ individual items of stuff. Why should we pick such an absurdly large number? Well it happens that $6.022 \times {10}^{23}$ individual ""^1H atoms have a mass of precisely $1.00 \cdot g$.

The mole is thus the link between the submicro world of atoms and molecules to the macro world of grams, and kilograms, and litres. This ties in with the notion of equivalence: to have a $16 \cdot g$ of $C {H}_{4}$ molecules, I need $6.022 \times {10}^{23}$ individual carbon atoms, and $4 \times 6.022 \times {10}^{23}$ individual hydrogen atoms.

It might be worthwhile if you spend some time on these ideas, because even at undergraduate level they seem to be poorly understood. And once you do get it, these sorts of problems are fairly trivial and straightforward.

So back to your problem, we know the number of particles. We don't know the molar mass of the particles. If you specify carbon, hydrogen, oxygen particles, then we can calculate the mass. Capisce?