Gas Laws

Charles’s Law 11.2

Charles’s Law

Temperature – Volume Relationship State “ the volume of a fixed mass of gas

varies directly with the Kelvin temperature at constant pressure.

Charles’s Law

Charles found that if the temperature of a gas at Oo C is increased by 1o C its volume increases by 1/273 of its original. So new volume would be

274/273 at 1o C

Charles’s Law

Must use Kelvin scale to get a directly proportional relationship

Charles’s Law

Mathematically V = kT or V1/T1 = V2/T2

Temperature MUST BE IN KELVIN!!!! Always convert Celsius to Kelvin before using the

above equation (Failure to do so = dire consequences to your GRADE!!!)

Pressure must be constant

Sample problem 1

A sample of neon gas occupies a volume of 752 mL at 25o C. What volume will the gas occupy at 50o C if the pressure remains constant?

Steps to Solve:1. Convert Temperatures to Kelvin(Celsius Temp + 273)

2. Rearrange equation to solve for V2

3. Insert Values into equation and Solve!

Ans = 815 mL Ne

Sample Problem 2

A helium balloon has a volume 2.75 L at 20.0oC. The volume of the balloon decreases to 2.46L after it is placed outside on a cold day. What is the temperature outside?

Steps to Solve:1. Convert Temperature to Kelvin (Celsius Temp + 273)

2. Rearrange equation to solve for T2

3. Insert Values into equation and Solve4. Reconvert to Celsius Degrees (Kelvin Temp - 273)

Ans = -10.9oC (262 K)

Sample problem 3

A gas at 65oC occupies 4.22 L. At what Celsius temperature will the volume be 3.87 L assuming the same pressure?

Ans = 37.0 oC

Answers to Sample Problems1. 815 mL Ne

2. -10.9oC (262 K)

3. 37.0 oC