Question

What is the volume expressed by a `74.3*g` mass of carbon dioxide at `294.9*K` enclosed in a piston at a pressure of `439*"mm Hg"`?

Answer 1

`V=(nRT)/P~=70*L`

Explanation:

The key to this question is to express the pressure, which is given in `"mm Hg"`, to atmospheres. We know (or should know) that `1*atm` will support a column of mercury that is `760*mm` high. Mercury columns (which are fast disappearing in laboratories these days) provides a highly visual and accessible measurement of pressures BELOW atmospheric.

And thus `P=("439 mm Hg")/("760 mm Hg"*atm^-1)=0.578*atm`

And thus `V=((74.3*g)/(44.0*g*mol^-1)xx0.0821*L*atm*K^-1*mol^-1xx294.9K)/(0.578*atm)`

`~=70*L`

Do the units in the calculation cancel out to give an answer in `L`? If not they should!