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Question

1.) A mass of 50.0 g of CO₂ gas occupies a volume of 20.0 L at a temperature of 35ºC. What is the pressure in torr of this gas?

2.) A chemical reaction produced 0.750 mol in chlorine gas (Cl₂) at 25ºC and 750 torr. What is the volume of the gas produced? (convert pressure to atmostpheres)

Answer 1

We will use the ideal gas law to find the pressure in atmospheres, and then convert it to torr.

PV = nRT

P = pressure = ?

V = volume = 20.0 L

n = moles = 50.0 g CO2 x 1 mol / 44 g = 1.136 moles

R = gas constant = 0.0821 Latm/Kmol

T = temperature in K = 35ºC + 273 = 308K

Solving for P we have

P = nRT/V = (1.136)(0.0821)(308) / 20.0

P = 1.436 atm x 760 torr/atm = 1092 torr = 1090 torr (3 sig. figs.)

Again, we'll use the ideal gas law:

PV = nRT and we'll solve for volume (V)

P = pressure = 750 torr x 1 atm/760 torr = 0.9868 atm

V = volume in L = ?

n = moles = 0.750

R = gas constant = 0.0821 Latm/Kmol

T = temperature in K = 25ºC + 273 = 298K

V = nRT/P = (0.750)(0.0821)(298) / 0.9869

V = 18.6 L (3 sig. figs.)