Charles's Law and the Combined Gas Law

Charles's Law and the Combined Gas Law

Charles's Law: Temperature and Volume

Charles's Law states that at constant pressure, the volume of a gas is directly proportional to its Kelvin temperature.

Charles's Law cont.

The straight line for the gas indicates that volume and temperature are in direct proportion.

Charles's Law cont.

When temperature increases, volume increases, and when temperature decreases, volume decreases.

Multiple Choice

According to Charles's Law when the temperature decreases the volume will

• decrease

• increase

• stay the same

Multiple Choice

According to Charles's Law, when the temperature increases, the volume will

• increase

• decrease

• stay the same

Kinetic Explanation of Charles's Law

As the gas particles are heated, they move faster and have more collisions with the sides of the container and move the piston upward creating an increase in volume.

Charles's Law cont.

The equation to the right can be used to find volume of temperature. The temperature in this equation must be in Kelvin degrees.

Multiple Choice

When using the formula for Charles law, temperature must be in

• Celsius

• Kelvin

• Fahrenheit

Charles's Law Sample Problem

A balloon is filled with 3.0 L of helium at 295 K and 1 atm. It is then placed outdoors on a hot summer day when the temperature is 304 K. If the pressure remains constant, what will the volume of the balloon be?

 $\frac{V_1}{T_1}$  = $\frac{V_2}{T_2}$              $\frac{T_2V_1}{T_1}$  =  $V_2$       $\frac{\left(304\ K\right)\left(3.0\ L\right)}{295\ K}$  =  $V_2$       

           
                                                                    3.1 L      = $V_2$ 

Multiple Choice

 A balloon is filled with 3.0 L of helium at 310 K and 1 atm. The balloon is placed in an oven where the temperature reaches 340 K. What is the new volume of the balloon?

 $\frac{V_1}{T_1}=\frac{V_2}{T_2}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \frac{T_2V_1}{T_1}\ =V_2$ 

• 0.92 L

• 4.2 L

• 3.3 L

Multiple Choice

A 4.0 L sample of methane gas is collected at 303 K. Predict the volume of the sample at 273 K.


 $\frac{V_1}{T_1}\ =\frac{V_2}{T_2}\ \ \ \ \ \ \ \ \ \frac{T_2V_1}{T_1}=V_2$  

• 3.6 L

• 4.4 L

• 2.3 L

Standard Temperature and Pressure

Some of the problems that follow will ask you to consider gases at standard temperature and pressure or STP. STP is defined as a temperature of 0.00°C or 273 K and a pressure of 1.00 atm.

Multiple Choice

Standard temperature is defined as

• 0.0 K

• 273 K

• 273°C

Multiple Choice

Standard pressure is defined as

• 1.00 atm

• 870 mmHg

• 0.00 atm

Combined Gas law

The combination of Boyle's Law and Charles's Law is called the Combined Gas Law

Determining Volumes at STP

A 154 mL sample of carbon dioxide gas is generated by burning graphite in pure oxygen. If the pressure of the generated gas is 1.18 atm and its temperature is 390 K, what volume would the gas occupy at standard temperature and pressure? (STP = 273 K and 1.00 atm)

 $\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}\ \ \ \Longrightarrow\ \ \ \frac{T_2P_1V_1}{T_1P_2}=V_2$  

 $\frac{\left(273K\right)\left(1.18atm\right)\left(154mL\right)}{\left(390K\right)\left(1.00atm\right)}\ =\ V_2$          $V_2\ =127\ mL$  

Multiple Choice

A 2.7 L sample of nitrogen gas is collected at 1.20 atm and 288 K. If the pressure increases to 2.00 atm and the temperature rises to 303 K, what volume will the nitrogen gas occupy?

 $\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}\ \ \ \Longrightarrow\ \ \ \frac{T_2P_1V_1}{T_1P_2}=V_2$ 

• 1.7 L

• 4.3 L

• 3.2 L

END