To determine how much calcium chloride has been used, you take a sample of slush from the
road to analyze.
You collect the following data:
Mass of empty container: 54.54 g
Mass of container and sample of slush:
160.65 g
Then, you evaporate the water from the solution
and determine the mass of the residue to be
3.16 g. What is the percent by mass of CaCl2 in
the slush that was collected?

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.