This question concerns the gas law and pressure.

Question

A SCUBA diver tank contains 12.00 L of air at a gauge pressure of 119.0 bar and a temperature of 22.00 degrees C.

a. Determine the number of moles of air in the tank.

b. Determine the volume this much air occupies at STP.

Answer 1

Ideal gas law: PV = nRT

P = pressure = 119.0 bar

V = Volume in liters = 12.00 L

n = moles = ?

R = gas constant = 0.083145 Lbar/Kmol

T = temperature in Kelin = 22.00ºC + 273.15 = 295.15K

Solving for n ...

n = PV/RT = (119)(12) / (0.083145)(295.15)

n = 58.19 moles (4 sig.figs.)

At STP, one mole of any ideal gas occupies 22.4 liters. This is a value you should learn/memorize. Therefore...

58.19 mols x 22.4 L / mole = 1303 L