Combined Gas Law
When is the Combined Gas Law used?
When Pressure, Volume, and Temperature of a gas all change.
A gas is 3.0 L at 298 K and 1.00 atm. What is its volume at 350 K and the same pressure?
3.52 L
After driving on the highway, your car's tires show a higher pressure than when they are cold. Why does this happen?
Because as the temperature of the air inside the tire rises, Pressure also increases if volume stays nearly constant.
What is 25°C in Kelvin?
298 K
The 3 laws used in the Combined gas law
Boyle’s Law, Charles’s Law, and Gay-Lussac’s Law
A gas is 500 mL at 1.2 atm and 300 K. What is the volume at 1.0 atm and 330 K?
594 mL
Why does your ear 'pop' when an airplane climbs to a higher altitude?
Pressure outside your ear decreases, so the gas inside expands
What pressure unit equals 1 atmosphere?
101.3 kPa
The amount of gas (in moles)
Calculate final pressure: 1.0 L of gas at 1.00 atm and 300 K is compressed to 0.5 L at 150 K.
4.00 atm
Why does a hot air balloon rise as it heats up?
The heated gas expands, increasing volume and decreasing density.
What happens to particles at 0 K?
They stop moving (theoretically)
Why is it that you get an incorrect answer because the ratio becomes mathematically invalid?
This happens if you forget to convert Celsius to Kelvin in a combined gas law calculation.
A 2.0 L gas at 250 K and 90 kPa is expanded to 3.0 L and heated to 375 K. What is the final pressure?
60 kPa
Why do scuba divers need to ascend slowly?
Rapid pressure decrease causes gas expansion, which can harm body tissues.
If temperature triples and pressure stays constant, what happens to volume?
Volume triples.
Why can't you use Celsius in gas law equations?
Because ratios require absolute temperature, which is only provided in Kelvin.
Solve for final temperature: A gas at 2.0 atm, 400 mL, and 300 K becomes 1.0 atm and 800 mL.
600 K
hy do cakes rise more when baked at high altitudes?
Lower external pressure lets gases expand more inside the batter.
What common mistake do students make with temperature in gas law problems?
Using Celsius instead of Kelvin.