Gas Laws

Gas Laws by: Amanda Applebaum, Lara Bonatesta

Boyle's Law

Gay-Lussac's Law

Charles's Law

At a constant temperature, gas pressure and volume are inversely related, which means as one increases, the other will decrease

The temperature and the pressure of a gas are directly related, meaning they both either increase or decrease at the same time. For this to occur, there has to be a constant volume and moles of gas

The volume of a gas is directly proportional to the Kelvin temperature, meaning both will increase or decrease at the same time. These conditions only apply however if the pressure is constant

Real-World Example

Scientific Example

Scientific Experiment

According to Gay-Lussac's Law as temperature increases pressure increases and as temperature decreases pressure decreases. In this experiment the beaker is filled with gaseous air molecules when the bottle is heated to molecules become energized and attempt to expand in volume but are unable to because they are trapped in the beaker. This increase in air pressure causes the water level under it to be pushed lower than the water level outside of it. As the candles burn they use some of the oxygen in the beaker for combustion producing Carbon Dioxide and water vapor which then fill up the top of the beaker forcing the oxygen down until the candles go out. When they go out the air molecules cool down and the pressure goes down causing for the need for balance and thus causing the beaker to fill up.

Sample Problems

In this lab experiment, a balloon is placed into a syringe. The hole at the bottom is covered and the syringe it squeezed together decreasing the volume and increasing the pressure causing the balloon to shrink. This exhibits Boyle's Law. The reverse effect occurs when the volume is increased, decreasing the pressure and causing the balloon to expand.

Real World Example

The baking of bread represents Charles's Law because during the baking process, yeast gives of carbon dioxide gas bubbles. These CO2 gas bubbles expand due to the increased temperature of the oven the bread is in, causing the volume of the bread to increase, which causes the bread to rise. The baking process shows how volume and temperature here have a directly proportional relationship

Real Life Example

The pressure in a sealed can of gas is 350 kPa at the temperature 340 K. If the can is further heated to 360 K, what will the new pressure in the can be?

Scientific Experiment

Sample Problem

One real life application of Gay-Lussac's Law is the firing of a bullet. When the gunpoweder burns a produces a large amount of very hot gas with a very high pressure, due to the relationship between temperature and pressure. This pressure pushes on the bullet and expels it out of the gun.

Sample Problem

When one breathes Boyle's Law is exhibited by the inverse relationship between pressure and volume of the thoracic cavity. When the intercostal muscles contract, lifting the ribs as the diaphragm contracts as well. This increases the volume of the thoracic cavity and decreases its pressure. It is then filled with air as the lungs inflate. The lungs continue to inflate until a pressure equilibrium is reached inside the lungs and outside the body. When the muscles relax, increasing pressure within the lungs causing it to be expelled, this is when one exhales.

A 400 mL sample of oxygen is heated at a constant pressure from 25 degrees Celsius to 79 degrees Celsius. What is the final volume?

At 3.4 atm, a sample gas takes up 5.2 L. If the pressure on the gas is increased to 8.0 atm, what will the new volume be?

1). Convert Temperatures:

• 25 C+273= 298 K
• 79 C+ 273= 352 K

(350 kPa)/(340 K)=(X kPa)/(360 K)

*(360 K) *(360 K)

(350 kPa)(360 K)/(340 K)=(X kPa)

370.588235= (X kPa)

In this lab experiment, a balloon is blown up and is enclosed in boiling water. The balloon from the heat begins to increase in size. Another balloon was also placed in a freezer, where after several hours, the balloon decreased in size. As this balloon begins to warm up again, it will slowly increase again. This exhibits Charles's Law, because with the first balloon, as the temperature increased, the balloon's volume increased (at a constant pressure). With the second balloon, as the temperature decreased, the balloon's volume decreased. Both experiments show this law's directly proportional relationship.

(400mL)/(298 K)= (V2)/(352 K)

(352 K) x (400mL/298 K)=V2

472.5=V2

The final volume is about 472.5 mL

(3.4 atm)(5.2 L)=(8.0 atm)(X L)

((3.4 atm)(5.2 L))/(8.0 atm)=(X)

2.21= X

The new volume would be 2.21 L

Avogadro's Law

Combined Gas Law

Dalton's Law of Partial Pressures

• This law uses concepts from the other gas laws
• If temperature remains constant, then Boyle's Law is applied
• P1 x V1 = P2 x V2
• If pressure remains constant, then Charles's Law is applied
• V1 / T1 = V2 / T2
• If volume remains constant, then Gay-Lussac's Law is applied
• P1 / T1 = P2 / T2

Avogadro's Hypothesis was that equal volumes of gases at the same temperature and pressure contain equal numbers of particles. The math relationship is directly proportional

• The total pressure inside a container is equal to the sum of the partial pressures of each gas.
• Partial pressure means any pressure distributed by the gas

Real-World Example

Sample Problem

The physical act of blowing up balloons represents Avogrado's Law because as more air particles are blown into the balloon, the volume of the balloon increases; this proves the directly proportional relationship between volume and the number of moles or particles

Illustration

The Equation

A 400 mL can of gas is at a pressure of 40 kPa. If the can is crushed or flattened by a school bus to a volume of 20 mL. What is the new pressure in kPa?

Scientific Experiment

Sample Problem

A container contains 2 moles of Ne, 5 moles of O2 and 3 moles of H2 at a total pressure of 1000 torr. Calculate the partial pressures.

How is the Equation Derived

7.00 L of an unknown gas contains 0.638 mol. If the amount of gas is decreased to 0.421 mol, what is the new volume?

V1=400 mL; P1=40 kPa; T=X; V2= 20 mL; P2=?

remove temperature from problem:its not given

P1V1=P2V2

(40 kPa)(400 mL)= (P2) (20 mL)

P2=800 kPa

XNe=nNe/nT=2/(2+5+3)=1/5=0.2

XO2=5/10=1/2=0.5

XH2=3/10=0.3

PNe= 0.2(1000)=200 torr

PO2=0.5(1000)= 500 torr

PH20.2(1000)=300 torr

• The P1 and P2 comes form the equation in Boyle's Law (multiplied by volume) and Gay Lussac's Law (divided by temperature)
• The V1 and V2 comes from the equation in Boyle's Law (multiplied by pressure) and Charles's Law (divided by temperature)
• The T1 and T2 comes from the equation in Charles's Law (divided into volume) and Gay-Lusacc's Law (divided into pressure)

200+500+300=1000

In this experiment, the students used soda that was most reactive with mentos (Sierra Mist) and conducted an experiment representing this law using balloons. They took one balloon and put it over the bottle with the Sierra Mist, and dropped the mento in. As a result, the solubility of the carbon dioxide in the soda decreases, causing an increase of moles of carbon dioxide in the bottle, which will then fill up the balloon (increasing its volume). This proves the hypothesis that volume and number of moles are directly proportional.

(7.00L)/(0.638mol)=(V2)/(0.421mol)

(0.421 mol) x (7.00L/0.638mol)=V2

4.62=V2

The new volume is about 4.62 L