Question

Question #d3749

Answer 1

The density of a gas depends on its mass and its volum (of course), which means that it depends on pressure and temperature.

When you are at STP, 1 mole of any ideal gas occupies exactly `"22.4 L"`. SInce no other information is given, you can safely assume that you are dealing with 1 mole of sulfur trioxide (`SO_3`).

Now, if you have 1 mole, we've established that you have a volume of `"22.4 L"` at STP. All you need now is its mass - for this use `SO_3`'s molar mass - `"80.1 g/mol"`.

This tells you that 1 mole of sulfur trioxide weighs `"80.1 g"`.

Therefore, the density of sulfur trioxide at STP is

`rho = m/V = ("80.1 g")/("22.4 L") = "3.58 g/L"`

This is a rather lengthy tutorial, but very good, it does not have the sulfur dioxide per se: http://www.eiu.edu/eiuchem/genchem/tutorial6.pdf