Ideal Gas Law and Density of a Gas
The Ideal Gas Law can also be used to determine the density of a gas. To derive that equation, we begin with the ideal gas law:
Density is defined as mass per unit volume.
Recall that we also derived the equation for the molar mass of a gas in the post Ideal Gas Law and Molar Mass of a Gas as:
To solve for g, we multiply each side by PV/RT:
The resulting equation is:
Plugging equation (5) into our equation for density (2):
Notice that volume V cancels out:
We now can use equation (7) to solve gas law problems for density.
What is the density of SO2 gas at 1.18 atm and 26 °C?
The gas law equation (7) for density is:
Wanted: ? Density
Molar mass of SO2 gas = 64.06 g/mol
P = 1.18 atm
T = 26 °C
We need to convert degrees Celsius to Kelvin:
Plugging these values into equation (7):
The density of of SO2 gas is 3.08 g/L.