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Welcome to Dr. Chu’s

Welcome to Dr. Chu’s

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Today’s

Today’s topic is …

GasesPart B: Gas Laws

Dr. Chu

River Dell Regional High School

GAS LAWS – THE START The barometer was

invented by Evangelisto Torricelli in 1643.

Barometer

The temperature scale

ANIMATION

Websites:• http://phet.colorado.edu/en/simulation/gas-

properties • http://www.mhhe.com/physsci/chemistry/

essentialchemistry/flash/gasesv6.swf

BOYLE’S LAW

Conditions: given amount of gas at constant temperature

Relationship: PV = constant

A sample of gas in a balloon is compressed from 7.00 L to 3.50 L. The pressure at 7.00L is 125 KPa. What will the pressure be at 2.50L if the temperature remains constant?

BOYLE’S LAW - EXAMPLE

CHARLES’ LAW

Conditions: given amount of gas at constant pressure

Relationship: V/T = constant

CHARLES’ LAW - EXAMPLE A gas sample at 20.0 C occupies a

volume of 3.00 L. If the temperature is raised to 50.0 C, what will the volume be if the pressure remains constant?

GAY-LUSSAC’S LAW

Conditions: given amount of gas at constant volume

Relationship: P/T = constant

The pressure of a gas in a tank is 4.00 atm at 200.0C. If the temperature rises to 280.0C, what will be the pressure of the gas in the tank?

GAY-LUSSAC’S LAW - EXAMPLE

COMBINED GAS LAW Combination of Boyle’s, Charles’, and

Gay-Lussac’s Laws. Relationship: PV/T = constant

COMBINED GAS LAW - EXAMPLE A gas at 70.0KPa and 10.0C fills a flexible

container with an initial volume of 4.00L. If the temperature is raised to 60C and the pressure is raised to 80.0 KPa, what is the new volume?

GENERAL STRATEGIES FOR SOLVING GAS LAW PROBLEMS Carefully read the problem and list all the

known and unknown parameters. Use the 1 and 2 for designations of start

and end states, respectively. Carefully label each parameter with 1 or 2 subscript to keep track.

If any of the three parameter is held constant, that parameter would have the same value for both states 1 and 2. Then the identical parameter can be cancelled from the combined gas law and individual gas laws reconstitute.

PROBLEM SOLVING STRATEGY – EXAMPLE 1 Submarines need to be extremely strong to

withstand the extremely high pressure of water pushing down on them. An experimental research submarine with a volume of 15,000 liters has an internal pressure of 1.2 atm. If the pressure of the ocean breaks the submarine forming a bubble with a pressure of 250 atm pushing on it, how big will that bubble be?

PROBLEM SOLVING STRATEGY – EXAMPLE 2 A gas that has a volume of 28 liters, a temperature

of 45 0C, and an unknown pressure has its volume increased to 34 liters and its temperature decreased to 35 0C. If I measure the pressure after the change to be 2.0 atm, what was the original pressure of the gas?

GAS LAWS – EXERCISE1. A gas takes up a volume of 17 liters, has a

pressure of 2.3 atm, and a temperature of 299 K. If I raise the temperature to 350 K and lower the pressure to 1.5 atm, what is the new volume of the gas?

2. A gas has a temperature of 14 0C, and a volume of 4.5 liters. If the temperature is raised to 29 0C and the pressure is not changed, what is the new volume of the gas?

3. If I have 21 liters of gas held at a pressure of 78 atm and a temperature of 900 K, what will be the volume of the gas if I decrease the pressure to 45 atm and decrease the temperature to 750 K?

GAS LAWS – EXERCISE (ANSWERS)1. A gas takes up a volume of 17 liters, has a

pressure of 2.3 atm, and a temperature of 299 K. If I raise the temperature to 350 K and lower the pressure to 1.5 atm, what is the new volume of the gas? [30.5L]

2. A gas has a temperature of 14 0C, and a volume of 4.5 liters. If the temperature is raised to 29 0C and the pressure is not changed, what is the new volume of the gas? [4.74L]

3. If I have 21 liters of gas held at a pressure of 78 atm and a temperature of 900 K, what will be the volume of the gas if I decrease the pressure to 45 atm and decrease the temperature to 750 K? [30.3L]