Gas Laws

Gas Laws

By Mihir Paranjape

Pressure

Pressure = Force/Area

Pressure in a gas is caused by the collisions of gas molecules with the walls of the container. The molecules are constantly moving in random directions and exert a force when they collide with a wall. Pressure is the result of millions of collisions occurring between the Gas molecules and the wall of the container. Faster the molecules move, the more force they will exert and cause an increase in pressure.

Pressure Conversions

There are many units of Pressure, we use atmospheres or atm in Chemistry.

Combined Gas Law.

A certain flexible weather balloon contains 5.9 L of helium gas. Initially, the temperature is 20.4^oC and the barometric pressure is 560.6 torr. The balloon then is taken to the top of Pike’s Peak, where the pressure is 400 torr and the temperature is 9.7^oC. What is the new volume of the balloon at the top of Pikes Peak?

Some text here about the topic of discussion

​	​1	​2
​P	​560.6	​400
​V	5.9​	​?
​T	20.4+273 = 293.4​	​9.7+273 = 282.7

​560.6 x 5.9 = 400 x V2

293.4 282.7​

3307.54 = 400 x V2

293.4 282.7​

V2 = 7.97 L​

Multiple Choice

You have a gas that has a pressure of 2 ATM and a volume of 10L.  What would be the new volume if the pressure was changed to 1 ATM?

• 5 L
• 20 L
• It would stay at 10L
• 1 L

Multiple Choice

A gas is at a pressure of 12 atm, a volume of 23 L, and a temperature of 200K. If the pressure is raised to 14 atm,  and the temperature is increased to 300K. What is the new volume of the gas?

• P1V1/T1 + P2V2/T2
• PV = nRT
• P1V1 = P2V2
• P1/T1 = P2/T2

Multiple Choice

What is the pressure of a car tire that had an initial pressure of 1.8 atm but was heated from 38°C to 123°C?

• 0.9 atm

• 2.1 atm

• 1.6 atm

• 3.4 atm

Ideal Gas Law

If we are given only one value of P, V or T, we are talking about the ideal gas law.

P = atm, V = L, T = K, R = 0.0821

n = number of moles of a gas.

​

You can plug the values in and solve for the unknown variable.

Make sure to convert all values into proper units.​

Ideal Gas Law

​A Flask with 5.9 L of volume at 6.1 psi Pressure contains 0.36 moles of a gas. What is the Temperature in the Flask in K?

​

P = 6.1 psi = 6.1/14.7 = 0.415 atm

V = 5.9 L

n = moles = 0.36

T = ?

0.415 x 5.9 = 0.36 x 0.0821 x T

T = 82.8 K​

Multiple Choice

If I have 4 moles of a gas at a pressure of 5.6 atm and a volume of 12 liters, what is the temperature?

• 204 K
• 200 K
• 2046 K
• 2000 K

Multiple Choice

Calculate the volume that a 0.323-mol sample of a gas will occupy at 265 K and a pressure of 0.900 atm.

• 7.18 L 
• 7.81 L
• 4.63 L
• 4.36 L

Multiple Choice

What pressure, in atm, is exerted by 2.50 L of gas containing 1.35 mol at 320 K?
PV=nRT

• 14.19 atm
• 16.53 atm
• 18.42 atm
• 22.54 atm