Question

Calculate the density of helium gas at 25.0â—¦c and at a pressure of 1521 mmhg. express your answer in g/l.

Answer 1

Ideal gas equation: pV = nRT

Transform it to show density:

pV = [mass/Molar mass] RT

mass/V = (p*molar mass) /(RT)

density = mass / V

density = p*molar mass / (RT)

Now susbtitute the data

p = 1521 mmHg * 1 atm / 760 mmHg = 2.0 atm
T = 25 °C + 273.15 = 298.15 k
molar mass of He = 4.0 g/mol
R = universal gas constant = 0.082 atm*L / mol*k

density =2.0 atm*4.0 g/mol / (0.082 atm*L / mol*k *298.15k)

density = 0.327 g/L