Unit 5 Kinetic Molecular Theory of GasesReview

Unit 5 Kinetic Molecular Theory of Gases

Kinetic Molecular Theory

An ideal gas is an imaginary gas that perfectly fits assumptions of the kinetic-molecular theory. Ideal gases assumptions:

Gas particles exert ______on one another.

Gas molecules are said to be in ______.

The volume of gas particles themselves is said to be ______.

The collisions between gas particles are ______.

The temperature of a gas is a measure of the average ______of the gas particles.

The 4 properties of an ideal gas are ______(n), ______(V), ______(P) and ______(T).

Real versus ideal gases

Real gases deviate from ideal at very ______or ______

Real gases have ______.

Real gases have may have attractive forces between molecules (intermolecular forces).

Real gases lose energy when particles collide.

Vocabulary

Boiling Point Contraction Diffusion Expansion EffusionLow DensityTemperature

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Unit 5 Kinetic Molecular Theory of GasesReview

  1. average kinetic energy1. ______
  2. the process of atoms moving further apart due to an increase in temperature2. ______
  3. spontaneous mixing of two or more gases 3. ______
  4. temperature at which a liquid changes to a gas4. ______
  5. the process of gas molecules moving from an area of high concentration to an area 5. ______

of low concentration

  1. the process of gas particles losing energy and occupying a smaller volume6. ______
  2. diffusion of a gas through a small opening 7. ______
  3. low gas particles per area; gases are mostly empty space8. ______

Pressure

Pressure is the ______per unit ______. Air pressure is the ______of the molecules hitting the sides of a container. Atmospheric pressure is measured using a ______. A ______is an instrument used to measure pressure in the laboratory.

1 atm = 101.3 kPa = 760 mm Hg = 760 torr = 14.7 psi

9.3 atm x ______= mm Hg

293 kPa x ______= mmHg

98 kPa x ______= atm

982 mm Hg x ______= psi

Temperature is the ______of a system. Standard temperature is equal to ______Kelvin or ______Celcius.

26.0 C = ______K400 K = ______C

100 K = ______C 135 C = ______K

-127 C = ______F 4° F = ______C

What is the temperature of a sample of gas that has doublethe kinetic energy (motion energy) of a sample of gas at 80C?

Gas Behavior

Using the unit vocabulary, explain each in terms of energy change and molecule movement.

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Unit 5 Kinetic Molecular Theory of GasesReview

  1. Describe the changes in heat energy and particle arrangement as dry ice sublimes.
  1. An aerosol can of air freshener is sprayed into a room. What happens to the pressure of the gas if its temperature stays constant?
  1. Why does the evaporation of sweat cool your body on a hot day?
  1. You are stranded in a blizzard. You need water to drink, and you are trying to stay warm. Should you melt snow and then drink it or just eat snow? Explain.

Brinkmann2011

Unit 5 Kinetic Molecular Theory of GasesReview

Gas Laws Summary

Gas Law

/ Definition / Variables / Constants / Equation
Boyle’s Law / At constant temperature, the volume of a gas is ______proportional to pressure. / P ↑ V ↓
P ↓V ↑ / Temp
moles / P1V1=P2V2
Charles’ Law / At constant pressure, the volume of a gas is ______proportional to its Kelvin temperature.
Gay-Lussac’s
Law / At a constant volume, the pressure of a gas is directly proportional to its Kelvin temperature.
Combined Gas
Law
Avogadro’s Law / At constant temperature and pressure, equal ______of gas contain the same number of ______.
Dalton’s Law of Partial Pressure / Pressure / Not applicable
Ideal Gas Law / Relates volume, temperature, pressure and amount of gasparticles to standard conditions.

Gas Law Application

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Unit 5 Kinetic Molecular Theory of GasesReview

Death Valley, California, has an elevation of 53 m below sea level. Explain how this altitude would affect the boiling point of water.

Explain why on a cold autumn morning a camper’s air mattress may appear to be somewhat flatter than it was when blown up the afternoon before. Assume no leaks.

What happens to the pressure of a gas in a light bulb a few minutes after the light is turned on?

The volume of air in human lungs increases before it is exhaled. What happens to the temperature of the air in the lungs to cause this change, assuming pressure stays constant?

Explain why placing a dented table tennis ball in boiling water is one way to remove the dent in the ball. Assume it has no holes.

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Unit 5 Kinetic Molecular Theory of GasesReview

BOYLE, CHARLES, GAY-LUSSAC, AND THE COMBINED GAS LAW

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Unit 5 Kinetic Molecular Theory of GasesReview

  1. A gas sample occupies 200 mL at 760 mm Hg. What volume does the gas occupy at 400 mm Hg?

Define variables:

Formula:

Show work:

Answer Question (Check work):

  1. 4. Nitrogen gas in a steel cylinder is under a pressure of 150 atm at 27°C. What will the pressure in the tank be of the tank is left in the sun and the internal temperature rises to 55°C?

Define variables:

Formula:

Show work:

Answer Question (Check work):

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Unit 5 Kinetic Molecular Theory of GasesReview

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Unit 5 Kinetic Molecular Theory of GasesReview

  1. An ideal gas occupies 400ml at 270 mm Hg and 65C. If the pressure is changed to 1.4 atm and the temperature is increased to 100C, what is the new volume?

Define variables:

Formula:

Show work:

Answer Question (Check work):

  1. A constant volume of oxygen is heated from 100C to 185C. The initial pressure is 4.1 atm. What is the final pressure?

Define variables:

Formula:

Show work:

Answer Question (Check work):

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Unit 5 Kinetic Molecular Theory of GasesReview

Brinkmann2011

Unit 5 Kinetic Molecular Theory of GasesReview

  1. A sample of 25L of NH3 gas at 10C is heated at constant pressure until it fills a volume of 50L. What is the new temperature in C?

Define variables:

Formula:

Show work:

Answer Question (Check work):

  1. A sample of 25L of NH3 gas at 10C is heated at constant pressure until it fills a volume of 50L. What is the new temperature in C?

Define variables:

Formula:

Show work:

Answer Question (Check work):

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Unit 5 Kinetic Molecular Theory of GasesReview

Ideal Gas Law

PV = nRT

P =

V =

n =

T =

  1. What is the volume at STP of a sample of CO2 that has a volume of 7.50 L at 30.0°C and 0.75 atm?

Define variables:

Formula:

Show work:

Answer Question (Check work):

  1. A 75.0 mL container holds 62 moles of gas at a temperature of 215° C. What is the pressure in atmospheres inside the container?

Define variables:

Formula:

Show work:

Answer Question (Check work):

  1. What is the volume of a sample of O2 that has a mass of 50.0 g and is under a pressure of 1.20 atm at 27.0°C?

Define variables:

Formula:

Show work:

Answer Question (Check work):

DALTON’S LAW OF PARTIAL PRESSURE

The ______pressure of gas in a container is equal to the sum of the ______.

  1. Gases A, B, and C occupy a container at a pressure of 4.5 atm. There are three times as many moles of Gas B as Gas A. There are a one fourth as many moles of Gas C as Gas A. Find the partial pressures of Gases A, B, and C.
  1. A sample of gas contains 4.5 moles N2, 6.5 moles O2, and 1 mole CO2. If the sample has total pressure of 98.5 kPa, what is the partial pressure of each gas.

Vapor Pressure of Water

Temp (ºC) / v.p. of water
(mm Hg) / Temp. (ºC) / v.p. of water
(mm Hg)
18 / 15.48 / 21 / 18.65
19 / 16.48 / 22 / 19.83
20 / 17.54 / 23 / 21.07

A sample of hydrogen gas was collected by displacement of water at 21ºC. The total pressure was 748 mm Hg. What pressure would the dry hydrogen exert in the same container?

A sample of oxygen was collected by displacement of water. The oxygen occupied 742 mL at 19ºC. The barometric pressure was 753 mm Hg. What volume would the dry oxygen occupy at STP?

Graham’s Law

Graham’s law of effusion/diffusion states that the rates of movement of gases at the same temperature and pressure are inversely proportional to the square roots of their molar masses.

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Unit 5 Kinetic Molecular Theory of GasesReview

Rate1 = rate of Gas 1

Rate2 = rate of Gas 2

M1 = molar mass of Gas 1

M2 = molar mass of Gas 2

Let Gas 1 be H2 and Gas 2 be O2.

Therefore, hydrogen molecules effuse four times faster than those of oxygen.

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Unit 5 Kinetic Molecular Theory of GasesReview

  1. If equal amounts of helium and argon are placed in a porous container and allowed to escape, which gas will escape faster and how much faster?
  1. List the following gases from the slowest to fastest. CO2Ar O2 Cl2 NO2

Consider the fragrance industry. Would we want our cologne or perfume to travel faster or slower. A lady may get more attention (the real purpose of fragrance) if it travels faster. However the fast traveling (low mass) fragrance would need to be applied more frequently. This is among the many things to be considered as a chemist in this industry.

Gas Laws and Stoichiometry

_____ Mg + _____ HCl → _____ H2 + _____ MgCl2

  1. If 20.2 grams of Mg react completely, how many liters of H2 gas are produced at STP?
  1. If 57 ml of H2 gas is produced at STP, what volume of 6 M HCl reacted?

____ KClO3(s) ______KCl(s) + ______O2(g).

  1. Solid potassium chlorate (KClO3) decomposes to produce solid potassium chloride (KCl) and oxygen gas (O2). What volume of oxygen gas, measured at 40.0°C and 650 mm Hg, will be produced when 13.5 g of potassium chlorate is decomposed?

Define variables:

Formula:

Show work:

Answer Question (Check work):

  1. Solid iron(II) chloride (FeCl2) is decomposed to produce solid iron (Fe) and chlorine gas (Cl2) according to the balanced chemical equation: FeCl2(s) Fe(s) + Cl2(g). What volume of chlorine gas, measured at 71.7°C and 1.33 atm, will be produced when 98.4 g of iron(II) chloride is decomposed?

Define variables:

Formula:

Show work:

Answer Question (Check work):

Challenge Problems

  1. A gas sample with a mass of 0.25 g occupies a volume of 85 ml a 150 OC and 720 mmHg. What is the approximate molar mass of this gas?

Define variables:

Formula:

Show work:

Answer Question (Check work):

  1. A 20.0 g nitrogen gas and 7.10 g of hydrogen gas is introduced into a 3.00 L container at 25°C. A spark is set off in the container and the container is cooled to 25° C.

The equation is N2(g) + 3H2(g)  2NH3(g)

  1. What was the pressure in the container before the reaction in atm?
  1. What is the limiting reactant?
  1. How much ammonia gas is produced (NH3)?
  1. What was the pressure of ammonia in the container after the reaction, in atm?
  1. What is the total pressure in the container after the reaction?

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