Question

What is the number of moles in a `1*L` volume of propane?

Answer 1

You have specified a volume of propane; we can go no farther without assumptions.

Explanation:

We need details of (i) the temperature, and (ii) the gas pressure, BEFORE we can calculate `n`, the number of moles. We might assume `298` `K` and `1` `atm`, but it is likely that the propane came in a bottle, in which case the assumption is invalid.