CP Chapter 13/14 Notes The Property of Gases Kinetic Molecular Theory

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1 CP Chapter 13/14 Notes The Property of Gases Kinetic Molecular Theory Kinetic Molecular Theory of Gases The word kinetic refers to. Kinetic energy is the an object has because of its motion. Kinetic Molecular Theory makes assumptions about: o Size o Motion o Energy of gas particles Kinetic Molecular Theory 1. According to the KMT all matter consists of tiny particles that are in constant, motion o Move in a line until they collide with other particles or with the walls of the container. 2. Gas particles are much than the distances between them. Most of a gas consists of space. o Because they are so far apart, there are no or forces between the gas molecules o The motion of one particle is of the motion of other particles 3. No kinetic energy is when gas particles collide with or with the walls of the container ( collision) o The total amount of kinetic energy remains. 4. All gases have the average kinetic energy at a given temperature o is a measure of average kinetic energy of particles in a sample of matter. o Kinetic energy and temperature are directly related o The the temperature, the the kinetic energy Absolute Zero The greater the atomic and molecular, the greater the is of a substance. If all atomic and molecular motion would, the temperature would be at zero ( Kelvin or o C) o C = Kelvin Diffusion and Effusion Diffusion describes the of one material through another o Particles diffuse from an area of concentration to concentration Effusion gas escapes through a tiny. o The heavier the molecule, the it will effuse or diffuse Pressure Pressure is the per unit area Gas pressure is the force exerted by a per unit surface area of an object. o Gas pressure is the result of billions of collisions of billions of gas molecules with an object Atmospheric pressure ( pressure) results from the collisions of molecules with objects. o The air pressure at altitudes is slightly lower than at sea level because the density of the Earth s atmosphere decreases as elevation increases. Vacuum - Empty space with particles and no pressure Measuring Pressure Barometer an instrument used to measure pressure Manometer an instrument used to measure gas pressure in a container Units of Pressure and STP Average atmospheric pressure is 1 atm STP (Standard Temperature and Pressure) o 1 atm and 0 o C or 1 atm and 273 K Conversion Factors for Pressure Example 1: Convert 2.5 atm into torr, mmhg and kpa. 1

2 Example 2: Convert 215 kpa into atm, mmhg, and torr. Dalton s Law of Partial Pressures Dalton s law of partial pressures states that the pressure of a mixture of gases is equal to the of the pressures of all the gases in the mixture. Example 1: A mixture of O 2, CO 2, and N 2 has a total pressure of 0.97 atm. What is the partial pressure of O 2, if the partial pressure of CO 2 is 0.70 atm, and the partial pressure of N 2 is 0.12 atm? Example 2: There is a mixture of CO2, O2, and CO in a container. What is the total pressure if the pressure in atm if O2 is atm, CO2 is 235 kpa, and CO is 455 torr? The Gas Laws proportional - as one variable goes the other goes as well. Both variables do the same thing. proportional - as one variable goes the other goes. The two variables do the opposite thing. Boyle s Law Pressure (P) and volume (V) are proportional. Temperature is V P 2

3 Example 1: A helium balloon was compressed from 4.0L to 2.5 L at a constant temperature. If the pressure of the gas in the 4.0L balloon is 210 kpa, what will the pressure be at 2.5L? A sample of neon gas occupies 0.200L at atm. What will be its volume at 29.2 kpa pressure? Charles s Law Volume (V) and temperature (T) are proportional. V Pressure is Temperature must be in Kelvin. T Example 1: A gas sample at 40.0 o C occupies a volume of 2.32 L. If the temperature is raised to 75.0 o C, what will the volume be, assuming the pressure remains constant? Example 2: A gas sample at 55.0 o C occupies a volume of 3.50 L. At what new temperature in Celsius will the volume increase to 8.00L? 3

4 Gay-Lussac s Law Pressure (P) and temperature (T) are proportional. P Volume is T Example 1: The pressure of a gas in a tank is 3.20 atm at 22.0 o C. If the temperature rises to 60.0 o C, what will be the gas pressure in the tank? Example 2: A rigid container has a gas at constant volume at 665 torr pressure when the temperature is 22.0 o C. What will the pressure be if the temperature is raised to 44.6 o C The Combined Gas Law Example 1: A gas at 110 kpa and 30.0 o C fill a flexible container with an initial volume of 2.00L. If the temperature is raised to 80.0 o C and the pressure increased to 440kPa, what is the new volume? Example 2: An unopened, bottle of soda contains 46.0 ml of gas confined at a pressure of 1.30 atm at a temperature of 5.00 o C. If the bottle is dropped into a lake and sinks to a depth at which the pressure and temperature changes to 1.52 atm and 2.90 o C, what will be the volume of gas in the bottle? 4

5 Avogadro s Principle Avogadro s principle states that volumes of gases at the same temperature and contain number of particles. The volume for a gas is the that one mole occupies at 0 o C and 1 atm or. This is equal to. STP (Standard Temperature and Pressure) = 1 mole of gas at STP = Example 1: Calculate the volume that mol of gas at standard temperature and pressure (STP) will occupy. Example 2: How many moles of oxygen gas will be contained in 5.00L flask at STP? Example 3: Calculate the volume that g of methane gas will occupy at STP. Example 4: How many grams of carbon dioxide gas are in a 0.75 L balloon at STP? Ideal Gas vs. Real Gas The Ideal Gas Law Ideal Gas Real Gas Follows gas laws under all conditions of Follows gas laws under some conditions of temperature and pressure. temperature and pressure. Follows conditions of the Kinetic Molecular Does conform to the Kinetic Molecular Theory (KMT) Theory. Real gases have a and An ideal gas does exist in real life attractive and forces. A real gas differs from an ideal gas the most at temperature and pressure. 5

6 Ideal Gas Law Ideal Gas Law Using Moles Example 1: Calculate the number of moles of gas contained in a 3.00L vessel at 298K with a pressure of 1.50 atm. Example 2 What pressure will be in kpa when there are mol of gas in a 5.00L container at 17.0 o C. Gas Stoichiometry When gases are involved, the coefficients in a balanced chemical equation represent not only molar amounts (mole ratios) but also relative volumes (volume ratios). C 3 H 8(g) + 5O 2(g) 3CO 2(g) + 4H 2 O(g) Example 1: What volume of oxygen gas is needed for the complete combustion of 4.00L of propane gas (C 3 H 8 )? Assume constant pressure and temperature. Example 2: How many liters of C 3 H 8 is needed to produce 8.00L of CO 2? Example 3: What volume of oxygen is needed to completely combust 5.67 L of methane gas (CH 4 )? Write and balance the equation. 6