An unknown gas has a molar mass of 201.3 gmol at 30∘C and 2.00 atm. What is its density?

Answer 1

MW = Molar mass = 201.3 g mol^-1

P = 2.00 atm

T = 30 °C + 273 K = 303 K

R = 0.0821 L atm mol^-1 K^-1

Using the ideal gas law equation, PV = nRT, we need to solve for the density, d = m / V or d = g / V.

In the ideal gas law equation, n = # of moles = g / MW. Substitute this equation into the ideal gas law equation, you get

PV = gRT / MW

Rearrange the above to obtain the equation in the form of g / V, which is your density.

g / V = P x MW / RT

g / V = (2.00 atm x 201.3 g mol^-1) / (0.0821 L atm mol^-1 K^-1 x 303 K)

g / V = 16.2 g/L = density

Answer 2

PV = nRT

This problem gives you T and P, R is a constant, but, without V a(volume), you can't solve for n.

If you could solve for n, the number of moles, you could use the molar mass given to calculate mass. D = m/vol

Ishwar has shown you how to calculate the density.