Question

The pressure gauge of a steel cylinder of methane gas () reads 400 psi. The cylinder has a volume of 1.90 L and is at a temperature of 20.0°C. How many grams of methane does the cylinder contain?

Answer 1

Answer – We are given, P = 400 psi , V = 1.90 L, T = 20.0^oC +273 = 293 K

Now first we need to convert the given pressure psi to atm

We know

1 psi = 0.0680 atm

400 psi = ?

= 27.2 atm

Now we need to use the Ideal gas law

PV =nRT

So, n = PV / RT

          = 27.2 atm *1.90 L / 0.0821 L.atm.mol^-1.K^­1*293 K

          = 2.15 moles

Now convert this moles to mass of methane

We know,

Mass = moles * molar mass

Mass of methane = 2.15 moles * 16.0426 g/mol

                             = 34.5 g

So, 34.5 grams of methane does the cylinder contain