Chapter 19

The Ideal Gas Equation

The Ideal Gas Equation

PV = nRT

• P = pressure • V = volume • n = number of moles • T = temperature • R =

gas constant

a

R values

A I

How many moles of gas will a 1250 cm 3 flask hold at 35.0



C and a pressure of 95.4 kPa?

0.0466 mol

What pressure in kPa is exerted by 0.00306mol of gas in a 25.9cm

3 container at 9.0

°C?

277 kPa

The Concorde, a supersonic passenger jet flew its last flight on November 26, 2003. It was a major pollution concern in that it produced 6.6 x 10 4 kg of CO 2 for each hour of flight at 42 kPa and 627 °C. How many liters of CO 2 is this?

The Concorde, a supersonic passenger jet flew its last flight on November 26, 2003. It was a major pollution concern in that it produced 6.6 x 10 4 kg of CO 2 for each hour of flight at 42 kPa and 627 °C. How many liters of CO 2 is this?

2.67 x 10 8 L = 267,000,000 L

Gram Formula Mass (Molar Mass)

• The ratio of grams per mole.

H 2 CO 2 = 2 g/mol = 44 g/mol H 2 O = 18 g/mol • We can therefore calculate gram formula mass if we know the

grams

and the

moles.

• GFM = grams/moles

A poisonous gas is leaking out of an old gold mine. A chemist collects 4.564 grams of the gas and uses the ideal gas equation to determine that this is 0.163 moles. Is the gas CH 4 , CO, or AsH 3

MM = 28 g/mol

Remember our first question today.

How many moles of gas will a 1250 cm 3 flask hold at 35.0



C and a pressure of 95.4 kPa?

•

n = PV / RT = 0.0466 mol 0.186 g of a gas at 35.0



C and 95.4 kPa occupies a volume of 1250 cm 3 . Is the gas H 2 , He, O 2 , or CO 2 ?

GFM = grams/mole = 0.186 g/0.0466 moles = 3.99 g/mol ≈ 4 g/mol Therefore the gas is most likely He.

1.00g of a gas occupies 0.820 dm 3 at 760 torr and 3.0

°C. The gas is most likely: (a) BH 3 (b) B 4 H 10 (c) B 2 H 6 (d) B 3 H 12 (e) B 5 H 14

Homework

•

Worksheet: The Ideal Gas Equation