Experiment Eight

Gas Laws

Procedural Tips

FAQs

Introduction/Goals

Background

Pre-lab

Additional Questions

Supplies and Chemicals

Safety Precautions

Waste Disposal

In this experiment you will investigate how the volume of a gas changes with temperature. The experimental change in volume will be compared to the expected change in volume (determined by using the combined gas law).

Print a copy of the Grading Sheet for this lab.

Procedural Tips:

Using the Bunsen Burner

Setting up a Boiling Water Bath

Equalizing Water Levels 

Construction of a Graph

Using the Thermocouples

FAQ:

Why do I have to wear safety goggles?

Introduction/Goals:

Introduction:

You will use the combined gas law to investigate the effect of changes in temperature and pressure on the volume of a gas. Dalton's law will be used because the total pressure in the flask at the end of the experiment is the pressure exerted by the air and the pressure of the water vaport.

Goals:

Background:

Boyle's law states that the volume that a fixed amount of gas will occupy is inversely proportional to the pressure of the gas, provided the temperature is kept constant. This relationship between pressure and volume is stated as

PV=k, where P=pressure, V=volume and k=a constant

Charles' law states that, at a constant pressure, the volume of a gas sample is directly proportional to the temperature of the gas. This behavior can be stated mathematically as:

V/T = k where V=volume, T=temperature and k=a constant

In this equation, the temperature must be expressed in kelvins. A Celsius temperature may be converted to kelvin by adding 273 to the Celsius temperature.

Boyle's Law and Charles' Law can be combined into a single equation called the combined gas law: P1V1/T1 = P2V2/T2. The combined gas law is useful because it allows for the effect of changes in temperature and pressure on the volume of a gas to be considered simultaneously.

Dalton's Law of Partial Pressures states that the total pressure exerted by a mixture of gases in the sum of the individual pressures exerted by each gas in the mixture. Dalton's Law will be used to determine the pressure of dry air by subtracting the pressures exerted by the water vapor from the atmospheric pressure.

Pre-lab

Read the introductory material on the webpage.

Read Experiment Eight in the laboratory manual.

Answer the pre-lab study questions  for Experiment Eight.

You are encouraged to do the Application Questions at the end of  Experiment Eight before coming to lab.

Additional Questions:

1. A cylinder of gas has a volume of 5.0 L at 90 atm pressure. What volume would the same gas have at the same temperature if the pressure were 1.0 atm?

2. A sample of nitrogen has a volume of 0.50L at 273K and 1 atm pressure. What is the volume at 350K and 1 atm?

3. A helium weather balloon filled at ground level and atmospheric pressure of 1.0 atm contains 50 L of gas at 20 °C. When it rises to the stratosphere, the external pressure will be 0.4 atm and the temperature will be -50 °C. What will the volume of the balloon in the stratosphere be?
4. A 1.0 L gas sample at 373K and 600 mm Hg. contains 50% argon and 50% helium. What are the partial pressures of the individual gases?
5. Answer question 8.117 in your McMurray textbook.

Supplies and Chemicals:

Safety Precautions:

SAFETY GOGGLES MUST BE WORN AT ALL TIME DURING THE LAB.

Use caution with boiling water.

Use caution when removing the flask from the boiling water and lowering it into the cold water bath.

Waste Disposal:

There are no specific waste disposal instructions for this experiment.