Calculate the density of sulfur hexafluoride gas at 261 oC and 352 torr. Use R = 0.0821 L-atm/mol-K for the value of the gas constant.

Answer 1

Since density is defined as mass / volume, all we need to do is assume we have 1 liter (volume) and then find the mass. To find the mass, we use the ideal gas law to find moles (n) and then convert moles to grams. Voila.

PV = nRT

P = pressure in atm = 352 torr x 1 atm/760 torr = 0.463 atm

V = volume in L = 1 L (we chose that volume)

n = moles = ?

R = gas constant = 0.0821 Latm/Kmol

T = temperature in K = 261C + 273 = 534K

Solving for n we have...

n = PV/RT = (0.463)(1) / (0.0821)(534)

n = 0.0106 moles of sulfur hexafluoride

molar mass sulfur hexafluoride (SF6) = 32 + 6x16 = 32 + 96 = 128 g/mol

mass of SF6 = 0.0106 moles x 128 g/mol = 1.36 g

DENSITY = 1.36 g / liter