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Copy of Gases
Transcript of Copy of Gases
& Gas Laws Boyle's Law Characteristics of Gases Kinetic Molecular Theory 1. Gas particles are solid spheres, really far apart
2. Gas particles are in constant rapid, random motion
3. Gas particles constantly collide with each other and with the walls of their container
4. Gas particle collisions are perfectly elastic
5. Avg. Kinetic energy is based on temperature (K) Pressure amount of force exerted per unit area of surface STP
Standard temperature and pressure
For a gas, the temperature is 0°C and 1.00 atm PV = k At 1.70 atm a sample of gas takes up 4.25L If the pressure is increased to 2.40 atm what will the new volume be? Charles's Law For a fixed amount of gas at constant pressure:
the volume of the gas increases as the temperature of the gas increases
the volume of the gas decreases as the temperature of the gas decreases Example: The volume of a gas is 625 L at a temperature of 0°C. If the temperature is increased to 80°C, what is the new volume? Ideal Gas Law the law states the relationship of pressure, volume, temperature, and the amount of gas in moles an ideal gas is one whose particles are infinitely small and do not interact with each other PV = nRT R = gas constant
8.314 L kPa/K mol
0.0821 L atm/K mol Miscellaneous Graham's Law of Diffusion
The rate of diffusion of a gas is inversely proportional to the square root of the gases density Effusion
The passage of gas under pressure through a tiny opening Diffusion
the movement of particles from regions of high density to regions of lower density Ideal gas law works with stoichiometry Example: At room temperature Xe atoms have an average speed of 240 m/s. At the same temperature, what is the speed of hydrogen molecules? Example: Liquid hydrogen and oxygen are burned in a rocket. What volume of water vaport at 555°C and 76.4 kPa, can be produced from 4.67 kg of liquid hydrogen? Temperature As you increase the Temp, the ___________ goes ______ Temp Energy Temp determines molecule speed. What is the difference between hot and cold days? Avg speed of molecules Force exerted by a gas as it collides with the container wall
That force gives basketballs their bounce and car tires inflated
1 atm = 101.325 kPa = 760 mmHg
= 760 torr What is pressure? Atmospheric Pressure Pressure exerted by ___________in the air 1 atm Higher altitude = ________ Pressure
STP = Standard Temperature and Pressure (0 Celsius or 273 K) T:
V: Temperature and Volume 1963 Charle's Law V T 1 2 V T 1 2 = T 1 2 T 1 2 V V Java Which of the following changes to a system WILL NOT result in an increase in pressure?
a. Raising the temperature
b. Increasing the volume of the container
c. Adding more gas molecules
d. Decreasing the volume of the container Four different flasks contain gas samples at 298 K. In which of the following samples will the gas molecules be moving the slowest?
d. N2 Gas pressure is caused by:
a. gas molecules colliding with surfaces
b. gas molecules hitting other gas molecules
c. gas molecules condensing to a liquid
d. barometers Which of the following gases would have the fastest rate of diffusion, assuming all of the gases are at the same temperature?
a. Kr - 84 amu
b. Ar - 40 amu
c. Ne - 20 amu
d. He - 4 amu Kelvin = 273K + C o Gases move in constant random motion
Particles are extremely far apart
The particles collide elastically (bounce)
Heat makes particles move faster (more pressure) KMT Summary K K What causes a basketball or soccer ball to be very firm? = Gases have mass.
Gases are compressible.
Gases fill their containers.
Gases exert pressure.
Pressure is related to Temperature Characteristics of Gas Essentially what Boyles law is saying is that pressure and volume are inversely related. Whats the general rule for boyle? 1 1 2 2 Imagine it is a beautifully sunny day at Punta Cana and you are at the beach, your scuba gear is packed in your car trunk, including your tank and you are just basking in the sun for a bit.
However when you return to your car, your scuba tank has exploded! Why?! what happened? Charles law explains why that happened. Your tank stayed at a constant volume but had an increase in temperature due to the hot sun, therefore the pressure increased and provided perfect conditions for an explosion. Try It or PV = k Boyles Law relates the pressure and volume of a gas that is held at constant temperature.
P V =P V
Where P=pressure, V=volume and the subscripts 1 and 2 represent the initial and final states. k = some constant rate Recall soda lab What are gases? How do they behave?
what characterstics do they have? A balloon contains 7.2 L of He. The pressure is reduced to 2.00 atm and the
balloon expands to occupy a volume of 25.1 L. What was the initial pressure
exerted on the balloon? 25.1 L 7.2 L Finish both worksheets on Boyle's and Charle's Laws and hand them in at periods end.
Make sure all gas laws formulas are in Kelvins
STP means Standard Temperature and Pressure
which stands for 1 atm, 273K Gay-Lussac's Law Charles' Law:
Gay-Lussac's Law If a gas is cooled from 323.0 K to 273.15 K and the volume is kept constant what final pressure would result if the original pressure was 750.0 mm Hg? If a gas in a closed container is pressurized from 5.0 atmospheres to 16.0 atmospheres and its original temperature was 25.0 °C, what would the final temperature of the gas be? Conversions: 1. Convert 0.875 atm to mmHg. 4. Convert 740.0 mmHg to kPa. 3. Convert 0.955 atm to kPa. 2. Convert 98.35 kPa to atm. 5. Convert 25.0 °C to Kelvin. 6. Convert 300K to °C Combined Gas Law Boyle's Law: Charle's Law Gay-Lussac's Law PV = PV V = V T T P = P T T A 40 L balloon is filled with air at STP (1atm, 273K). The balloon is tied to a rock and thrown into a cold body of water where it sinks to a temperature of 4 degrees celsius and a pressure of 11 atm. What will the new volume be at those levels? Combined Gas Law Carbon dioxide occupies a 2.54 L container at STP. What will be the volume when the pressure is 150 kPa and 26 Celsius http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/gasesv6.swf Gas Laws in Action: workers steam cleaned this tanker car and then sealed up the container, they came back the following morning to this.... http://www.brainpop.com/science/matterandchemistry/moles/ A an 800L tanker car is filled with nitrogen gas at 101.3 kPa. If the tanker car rises in the side of a mountain track the pressure will drop to 87.2 kPa. What will the new volume of gas in the tanker if the temperature drops from 25 Celsius to 8 Celsius.
If the sealed tanker can only hold 870L maximum, what would happen? why? What happened?
Why? Identify Law you need Identify possible variables Plug in variables Solve for missing piece Real examples? How do you know which law to use? Boyle's Charle's Gay- Lussac's Combined Gas Law Which Law? size of bubbles as they rise to the surface sea creatures brought to surface Popping of ears at high altitude max 1,100 atm We'll use the ____________ gas law for this because... How can we tell? ignited gunpowder forces projectile from barrel Tire explodes on extremely hot day add 1 atm per ____ meters down For each gas law:
a. Boyle's Law
b. Charle's Law 5. Give your own example of the combined gas law in real life. 1. summarize each in a few words, give a new real-world example for each 2. write the formulas for each law 3. make a very simple problem without specific units to show the relationship between each. (P & V, P & T and V & T) 4. the combined gas law uses all three laws in one, write that law's formula: On a piece of paper, write the ANSWERS to the following and hand it in when done. c. Gay Lussac's Law Pressure How'd ya do?
6. c Gay-Lussac's Law states
that the pressure of a
sample of gas at constant
volume, is directly
proportional to its
temperature in Kelvin. What is Gay-Lussac’s Law? P1 is the initial pressure
T1 is the initial temperature (in Kelvin)
P2 is the final pressure
T2 is the final temperature (in Kelvin)
Mathematically Gay-Lussac’s Law can be
expressed as P1 = P2
T1 T2 A tank of gas has a pressure of 2.75 atm at 20°C. What will be the new pressure in the tank if its temperature is increased to 100°C?
T2: Gay-Lussacs’s Law Practice Problems A gas system has initial pressure of 793 kPa and temperature of 34.5°C If the pressure changes to 446 kPa, what will the resultant temperature be in K?
T2: Do Now:
Write the Mathematical formulas for Charles's Law and Gay-Lussac's law
Predict what happens when Liquid Nitrogen is heated in a closed bottle by explaining whats happening molecularity How NOT to... Do Now: Warm UP