Start with this equation: density=molecular weight g/mol ÷ 22.4 L/mol. The molecular weight of carbon dioxide is 44.01 g/mol as calculated from the molecular weights of its individual elements.
Plug the molecular weight of carbon dioxide into the equation: density (g/L) = 44.01 g/mol ÷ 22.4 L/mol.
Solve the equation. The solution should be density = 1.9647 g/L.
Use an accurate thermometer to measure the temperature of the room. Record this temperature in a notebook.
Use a barometer to measure the pressure of the room. Record this pressure in a notebook.
Three equations are used to determine the density: the ideal gas law equation (PV=nRT), the equation for density (d = m÷V), and the equation used to determine the number of moles of a substance (n= m÷MW).
P is pressure in atmospheres (atm), m is mass, d is density, n is number of moles (a unit used to describe the amount of a substance), MW is molecular weight, V is volume in liters (L), T is the temperature (degrees Kelvin), and R is the gas constant (0.0821 L x atm /K).
Arrange and substitute the ideal gas law equation so that it becomes an equation for density. Start by substituting n for m÷MW so that the ideal gas equation becomes PV= mRT÷MW.
Since density = m÷V, rearrange the equation to solve for density like so:
PMW÷RT = m÷V. Therefore, density = PMW÷RT.
Solve the equation using your measured atmospheric pressure and temperature, the gas constant and the molecular weight of carbon dioxide (44.01 g/mol).
For example: measured pressure= 0.999 atm; measured temperature= 21.0 degrees Celsius + 273.15 = 294.15 Kelvin; density = PMW÷RT; density = (0.999 atm)(44.01 g/mol) ÷ (0.0821 L x atm/K)(294.15 K); density= 0.15 g/L.