STAAR Ladder to Success

Rung 4

Boyle’s Law• The pressure and volume of a gas

are inversely related – at constant mass & temp

P1V1 = P2V2

Charles’ Law• The volume and absolute

temperature (K) of a gas are directly related – at constant mass & pressure

V1T2 = V2T1

Dalton’s Law

• The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases.

Ptotal = P1 + P2 + ...

Avogadro’s Principle

• Equal volumes of gases contain equal numbers of moles– at constant temp & pressure– true for any gas

1 mol = 22.4 L

Ideal Gas Law

PV=nRT

You don’t need to memorize these values!

STP

Standard Temperature & Pressure

0°C 273 K

1 atm 101.325 kPa-OR-

STP

Example #1

• The pressure on a balloon with a volume of 300 mL increases from 1.10 to 2.00 atm. Calculate the new volume of the balloon.

Example #2

• The air in a balloon with a volume of 25 L is heated from 20 C to 60 C. If the pressure stays the same, what will be the new volume of the balloon?

Example #3

• A sample of gas in a 1L flask at 1.5 atm contains 75% CO2 and 25% H2O gas. Calculate the partial pressures of each gas.

Example #4

• Calculate the temperaure of 5.85 mol N2 gas in a 12 L steel bottle under 10 atm of pressure.

Gas Stoichiometry• Moles Liters of a Gas:

–STP - use 22.4 L/mol –Non-STP - use ideal gas law

• Non-STP–Given liters of gas?

• start with ideal gas law–Looking for liters of gas?

• start with stoichiometry conv.

Example #1

• What is the mass of oxygen gas produced when 29.2 g of water is decomposed by electrolysis according to the balanced equation?

2H2O 2H2 + O2

Example #2

• What volume in L of nitrogen dioxide gas is produced when 34 L of oxygen gas react with an excess of nitrogen monoxide? Assume conditions of STP.

2NO + O2 2NO2

Kinetic Molecular Theory

• Gases are made of molecules in constant, random motion

• The volume is small• Collisions are elastic• Forces (attractive and repulsive) are small• Average kinetic energy is proportional to

temperature