Question

If 37.5 mol of an ideal gas occupies 38.5 Lat 85.00°C, what is the pressure of the gas?

Answer 1

`P~=29*atm`

Explanation:

`P=(nRT)/V` `=` `(37.5*cancel(mol)xx0.0821*cancelL*atm*cancel(K^-1)*cancel(mol^-1)xx358.15*cancelK)/(38.5*cancelL)`

Note that the equation is consistent dimensionally. We wanted an answer in `"atmospheres"` and we got one.

When we do equations like this, the gas constant `R` can have many different values, each with different units. For chemists, probably the most useful one is `R=0.0821*L*atm*K^-1*mol^-1`. These need not be learned, because they will appear as supplementary material on the exam paper. They do have to be used correctly.