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Unit 8- BEHAVIOR OF GASES, boyles, charles.ppt

The document summarizes key concepts about the behavior and properties of gases, including: - Gases have no definite shape or volume and expand to fill their container. Their volume can be easily compressed. - The gas laws (Boyle's, Charles', Gay-Lussac's, Combined, and Ideal) describe the relationships between the pressure, volume, temperature, and amount of gas. - Dalton's Law states that in a gas mixture, the total pressure is equal to the sum of the partial pressures of the individual gases. - According to Graham's Law, the rates of effusion and diffusion of gases are inversely proportional to the square roots of their molar masses.

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BEHAVIOR OF GASES Unit 8 Chemistry Langley **Corresponds to Chapter 14 in the Prentice Hall Chemistry Book
PROPERTIES OF GASES  No definite shape/volume  Expands to fill its container  Easily compressed (squeezed into a smaller container)  Compressibility is a measure of how much the volume of matter decreases under pressure  Gases are easily compressed because of the space between the particles in a gas
PROPERTIES OF A GAS  Factors Affecting Gas Pressure  Amount of Gas  Increase amount, increase pressure  Volume  Reduce volume, increase pressure  Temperature  Increase temperature, increase pressure  Relationship between pressure, temperature, and volume is explained through the Gas Laws
GAS LAWS  Boyle’s Law  Charles’ Law  Gay-Lussac’s Law  Combined Gas Law  Ideal Gas Law  Dalton’s Law of Partial Pressure  Graham’s Law
BOYLE’S LAW  If the temperature is constant, as the pressure of a gas increases, the volume decreases  For a given mass of gas at constant temperature, the volume of a gas varies inversely with pressure  As volume goes up, pressure goes down  As volume goes down, pressure goes up  P1V1 = P2V2
BOYLE’S LAW  Real Life Example  As you push on the end of a syringe, the volume inside the syringe decreases as the pressure on the syringe increases  Mathematical Example 1:  P1 = 758 torr V1 = 5.0L P2 = ? V2 = 3.5L
BOYLE’S LAW  Mathematical Example 2  If 4.41 dm3 of nitrogen gas are collected at a pressure of 94.2 kPa, what will the volume be for this gas at standard pressure if the temperature does not change?
CHARLES’ LAW  As the temperature of an enclosed gas increases, the volume increases, if the pressure is constant  The volume of a fixed mass of gas is directly proportional to its Kelvin temperature if the pressure is kept constant  As volume goes up/down, temperature goes up/down  V1 = V2 Temperature must be in Kelvin! T1 T2
CHARLES’ LAW  Real Life Example  Balloon Lab-As the temperature of the water is increased, the volume of the balloon is increased.  Coke Can-Fill a coke can with a small amount of water, as you heat the water inside to near boiling, immediately invert the coke can into ice-cold water so the coke can is experiencing a dramatic drop in temperature, volume of can will decrease (can will crush in on itself)
CHARLES’ LAW  Mathematical Example 1  V1 = 250mL T1 = 300K V2 = 321mL T2 = ?  Mathematical Example 2  With a constant pressure, the volume of a gas is increased from 15.0L to 32.0L. If the new temperature is 20.0°C, what was the original temperature?
GAY-LUSSAC’S LAW  As the temperature of an enclosed gas increases, the pressure increases, if the volume is constant  The pressure of a gas is directly proportional to the Kelvin temperature if the volume remains constant  P1 = P2 Temperature must be in Kelvin! T1 T2
GAY-LUSSAC’S LAW  Real Life Example  Tires  The faster a car goes, the higher the temperature of the tire gets and the higher the pressure inside the tires  Mathematical Example 1  P1 = ? T1 = 456K P2 = 789mmHg T2 = 326K
GAY-LUSSAC’S LAW  Mathematical Example 2  The pressure in a tire is 1.8 atm at 20°C. After a 200 mile trip, the pressure reading for the tire is 1.9 atm. What is the temperature inside the tire at that new pressure?
COMBINED GAS LAW  Combines Boyle’s, Charles’, and Gay-Lussac’s laws  Describes the relationship among temperature, pressure, and volume of an enclosed gas  Allows you to perform calculation for situations IF and ONLY IF the amount of gas is constant  P1V1 = P2V2 Temperature must be in Kelvin! T1 T2
IDEAL GAS LAW  When you need to account for the number of moles of gas in addition to pressure, temperature, and volume, you will use the Ideal Gas Equation  Modified version of the Combined Gas Law  PV = nRT  n = number of moles  R = ideal gas constant  0.08206 (L-atm/mol-K)  62.4 (L-mmHg/mol-K)  8.314 (L-kPa/mol-K)
IDEAL GAS LAW  Mathematical Example 1  What is the pressure in atm exerted by 0.5 moles of N2 in a 10L container at 298 Kelvin?  Mathematical Example 2  What is the volume in liters of 0.250 moles of O2 at 20°C and 0.974 atm?
IDEAL GAS LAW  Mathematical Example 3  What is the temperature of 76 grams of Cl2 in a 24L container at 890mmHg?  Mathematical Example 4  A deep underground cavern contains 2.24x106L of CH4 at a pressure of 1.50x103kPa and a temperature of 315K. How many kilograms of CH4 does the cavern contain?
IDEAL vs. REAL GASES  Ideal gases follow the gas laws at all conditions of pressure and temperature  Conforms exactly to the all the assumptions of the kinetic theory (no volume, no particle attraction)doesn’t exist  Real gases differ mostly from an ideal gas at low temperature and high pressure  Under other conditions, behave as an ideal gas would
DALTON’S LAW  In a mixture of gases, the total pressure is the sum of the partial pressure of the gases  Partial pressure is the contribution each gas in a mixture makes to the total pressure  At constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the component of gases  Ptotal = P1 + P2 + P3 + …
DALTON’S LAW  Mathematical Example 1  In a container there are 4 gases with the following pressures: Gas 1-2.5 atm, Gas 2- 1.9 atm, Gas 3-798 mmHg, Gas 4-2.1 atm; find the total pressure in the container.
DALTON’S LAW  Mathematical Example 2  In a sample of HCl gas, the pressure of the gas is found to be 0.87 atm. If hydrogen makes up 34% of the gas, what is the pressure of the hydrogen?
GRAHAM’S LAW  The ratio of the speeds of two gases at the same temperature is equal to the square root of the inverted molar masses  The relative rate of diffusion  Diffusion is the tendency of molecules to move toward areas of lower concentration to areas of higher concentration until the concentration is uniform throughout  Gases of lower molar mass diffuse and effuse faster than gases of higher molar mass  Effusion is when gas particles escape through tiny holes in a container
GRAHAM’S LAW  √(Molar MassB/Molar MassA)  The rates of effusion of two gases are inversely proportional to the square roots of their molar masses  Use periodic table to get molar masses
GRAHAM’S LAW  Mathematical Example 1  What is the ratio of the speeds of Helium compared to Oxygen?  Mathematical Example 2  If Co2 has a speed of 22 m/s at 20°C, what is the speed of HCl at the same temperature?