Units and At the Molecular Level: Solid, Liquid, and Gas
Volume, Pressure, and Temperature and Random
The Gas Laws
The Ideal Gas Law
Gas Behavior
100
What are the units for the following when talking about these specific gas laws (there may be more than one units for each one):
1. pressure
2. volume
3. mass
4. temperature
1. atmospheres (atm) and kilo-Pascals (kPa)
2. liters and milliliters
3. grams (used as molar mass usually in the law formulas)
4. Kelvin (K) and Celsius (degrees C)
100
Define...
1. Pressure
2. Volume
3. Temperature
1. forces exerted by gas on the walls of the container.
2. the amount of space a given object takes up or occupies.
3. the average (kinetic) energy of moving molecules. The faster the molecules move, the higher the temperature becomes.
100
Define Gay-Lussac’s Law while incorporating what remains constant and the formula, and solve for P2 if given…
P1: 10 atm
T1: 50 degrees Celsius
T2: -20 degrees Celsius
Pressure can vary with temperature when there is a fixed (constant is both volume and amount of gas) volume of gas.
(P1/T1)=(P2/T2)
T1:253 K
T2:323 K
P2= P1(T2/T1)
P2= 12.76 atm
100
When the pressure is in the atmospheres (atm), what is the value of the Ideal Gas Constant?
.0821 L*atm/mol*K
100
What is unique about gases from solids and liquids?
Gases can expand to fill their container, can easily squeeze into a smaller volume, consider pressure, volume, temperature, and moles (also for solid and liquids). Gases molecules are spread farther apart and generally have more energy.
200
Explain and contrast the different molecular-kinetics of the three states: solid, liquid, and gas.
The Kinetic Molecular Theory states the behavior of matter (particles -- size, energy too) in motion.
Solid: molecules are very close and compact, strong forces between the molecules, least kinetic energy.
Liquid: molecules are closer together than gas state molecules and less close together than solid state molecules, strong forces, has the “middle” amount of energy between the three states.
Gas: molecules are farther apart, weak forces, and the gas state has the most energy. 
200
Explain what the Kinetic Molecular Theory is and use it to explain what happens when there is an increase in gas collisions.
The Kinetic Molecular Theory states that gases consist of tiny particles, atoms or molecules. The particles are so small, compared with the distances between them that the volume can be seen as zero. The particles are in constant random motion, colliding with the walls of the container and other particles around them. Collisions on walls cause pressure. The average kinetic energy of the gas particles is directly proportional to the Kelvin Temperature of the gas.
If there is an increase in gas collisions, there will be an increase in pressure too because there will be more force exerted on the walls.
200
Given this formula, P1*V1=P2*V2, what is the constant and what law does this formula reflect?
and list all the possible formulas for P1, V1, P2, V2.
Temperature and amount of gas are the two constants, Boyle’s Law.
P1:(P2*V2)/V1
V1: (P2*V2)/P1
P2:(P1*V1)/V2
V2:(P1*V1)/P2
200
What units make the ideal gas constant, and if given “R”, how do you solve for moles if you’re given:
Temp: 28 degrees Celsius
Pressure: 197 atm
Volume: 20.0 L
In order to get R, you have to multiple pressure and volume, divided by the product of number of moles and temperature (in Kelvin). Don’t forget to convert to Kelvin! 28+273=301
(197)(20)=(n)(.0821)
159 mol!
200
What are three variables that effect the kinetic energy of a molecule?
Also known as the kinetic molecular theory.
Particle size: farther apart (the smaller they are), they experience no significant attractive or repulsive forces
Particle motion: carry kinetic energy, collisions result in a transfer of kinetic energy.
Particle energy: based on mass and velocity, temperature is also dependent.
300
Define what direct and inverse relationships are and then incorporate both relationships in the Gas Laws, make sure you explain and give examples of each.
Direct Relationship: as one variable increases, the other does too.
Inverse Relationship: as one variable increases, the other decreases.
Boyle's Law- P and V hold an inverse relationship. When V goes down, P goes up. P*V is a constant (k).
Charles' Law- V and T are directly proportional.
Gay-Lussac's Law- P and T are directly proportional
300
With a fixed amount of gas, what will happen
1. When you increase volume...
2. When you decrease volume...
3. When you keep volume constant...
1. pressure decreases (temperature constant), temperature increase (pressure constant)
2. pressure increases (temp constant), temperature decrease (pressure constant)
3. Gay-Lussac's Law!
300
Apply Graham’s Law to find the rate of effusion between carbon dioxide and nitrogen (N2)?
List the formula and explain how the molecules spread normally.
Around 1.77
R1/R2 = (square root (M2/M1))
High concentration to low concentration.
Graham's Law of Diffusion:The speed of a gas particle is inversely related to the square root of its mass. Any to gas particles at the same temperature their KE avg is equal.
300
Using the Ideal Gas Law, find the volume in liters (L) based on the given information.
Temp: 165 K
Pressure: 0.75 atm
Moles: 0.312 mol
Volume = 5.635 L
V=(n*R*T)/P
300
What is the difference in having a non flexible container to a flexible container when it comes to maintaining different internal and external pressures?
Non flexible containers allow for both internal and external areas to have different pressures. Flexible containers cause the internal and external pressures to be the same because they are pushing on the sides of the container, eventually evening out.
400
You may get questions that give you needed information with units that need to be converted... Which laws require which units for temperature, volume, and pressure?
Gay-Lussac's Law: atm (pressure), K (temperature).
Charles's Law: L (volume, K (temperature).
Boyle's Law: L (volume), atm (pressure).
Combined Gas Law: L (volume), kPa (pressure), K (temperature).
400
With a fixed amount of gas, what will happen
1. When you increase temperature...
2. When you decrease temperature...
3. When you keep temperature constant...
1. Volume increases as well as pressure.
2. decrease pressure if volume is constant, volume decrease with constant pressure.
3. Boyle's Law!
400
Define the Combined Gas Law, state the units and give all of the formulas for..
P1, V1, T1, P2, V2, T2
The relationship among pressure, temperature, and volume of a fixed amount of gas (constant) The units for pressure are kPa, temperature is K, volume is liters (L).
P1: (P2*T1*V2)/(T2*V1)
V1:(P2*T1*V2)/(T2*P1)
T1:(P1*T2*V1)/(P2*V2)
P2:(P1*T2*V1)/(T1*V2)
V2:(P1*T2*V1)/(P2*T1)
T2:(P2*T1*V2)/(P1*V1)
400
List all the formulas for finding volume, pressure, moles, temperature, and the ideal gas constant.
Volume:V=(n*R*T)/P
Pressure: P= (n*R*T)/V
Moles: n= (P*V)/(R*T)
Temperature: T= (P*V)/(n*R)
Ideal Gas Constant: R= (P*V)/(n*T)
400
Compare the the two terms of movement of molecules of one material into different areas.
Give examples of each.
Diffusion: movement of one material through another, particles will diffuse from an area of high concentration to an area of low concentration. If someone sprays perfume in a certain area around them, in a matter of time soon people around the room will start to pick up the perfumes scent.
Effusion: gas escaping through a tiny opening. Occurs when there is a puncture in a container. If you poked a whole in a balloon, the air would come rushing out.
500
How do you convert the following...
1. Celsius to Kelvin
2. Milliliters to Liters
3. kiloPascals to atmospheres
4. atmospheres to mmHg
5. kilopascal to mmHg
6. mmHg to torr
7. torr to atmosphere
1. x (Celsius) + 273.15 = x (K)
2. 1 (milliliter) = .0001 (liter)
3. 1 (kPa) = .0098 (atm)
4. 1 (atm) = 760 (mmHg)
5. 1 (kPa) = 7.5 (mmHg)
6. 1 (mmHg) = 1 (torr)
500
With a fixed amount of gas, what will happen
1. When you increase pressure...
2. When you decrease pressure...
3. When you keep pressure constant...
1. volume decreases. If volume is constant, temperature will increase.
2. volume will increase. If there's a constant volume, temperature will decrease.
3. Charles' Law!
500
In what situation do you use Charles’ Law? What is the constant? If the starting volume of a gas is .5 L at 100K, what temperature is required if you increase the volume by 30%?
You use Charles’ Law in the case of constant pressure while trying to find either volume or pressure from two trials. This law states that the volume of gas is directly proportional to its kelvin temperature (with the constant being pressure and amount of gas).
(V1/T1)=(V2/T2)
.3*.5=.65
.65(100/.5)=
130 K
500
1. Find the mass of C3H8 (propane gas) if given:
Volume: 2 L
Pressure: 1 atm
Temp: -15 degrees C
2. Define what Density is and how it relates to mass, and give the Ideal Gas Law formula of how to find Density
1. Use M= (m*R*T)/(P*V)
Where M is molar mass and m is mass…
-15 C is converted into 258K
Molar mass of propane= 44 g/mol
Mass = 4.15 g
2. Density is mass per unit volume. The formula is D=(M*P)/(R*T)
500
List the STP (hint: standard temperature, pressure and molar volume)
