Question

Determine the density of oxygen gas (O2) at 25.0°C and 1.00 atm pressure.

Answer 1

Apply Ideal gas law

PV = nRT

where, P = pressure, V = volume of gas, n moles of gas, R ideal gas constant, T absolute T

T = 25C = 298K, P = 1 atm

now, we also know that

n = mass/MW

substitute

PV = mass/MW*RT

also, we need Density so

D = mass/volume

mass/V = P*MW/(RT)

D = P*MW/(RT)

now,

P = 1 atm is OVERALL pressure, but we need P = pressure of Oxygen

air has 21% approx of Oxygen

P-O2 = 0.21*Ptotal = 0.21*1atm = 0.21 atm of O2

MW = molar mass of Oxygen = 32 g/mol

now, substitute in data

D = P*MW/(RT)

D = (0.21)(32)/(0.082*298)

D = 0.27500409 g/L

D = 0.27500409 g of O2 / L