Gas Laws in Chemistry

Question

If a 23.1 g sample of nitrogen gas has a volume of 870 mL at 27.2 ˚C, what is its pressure in mm Hg? 

Answer 1

Ideal Gas Law: PV = nRT

P = pressure = ?

V = volume in liters = 870 ml x 1 L / 1000 ml = 0.870 L

n = mols of N₂ = 23.1 g x 1 mol N₂ / 28 g = 0.825 mols N₂

R = gas constant = 62.36 L-mm Hg / Kmole (note units of mm Hg to get out answer in mm Hg)

T = temperature in Kelvin = 27.2ºC + 273 = 300.1

Solving for P, we have ...

P = nRT / V

P = (0.825)(62.36)(300.1) / 0.870

P = 17,752 mm Hg = 17,800 mm Hg (3 sig. figs.)