Gases Flipbook

Gases Flipbook Rachel Comstock 4A



Table of Contents 1. Kinetic Molecular Theory 2. Volume, Temperature, and Pressure 3. Ideal Gas Law 4. Avogadro’s Principle and Molar Volume 5. Boyle’s Law 6. Charles’ Law 7. Gay-Lussac’s Law 8. Combined Gas Law 9. Practice Problems 10. Practice Problems Continued

Kinetic Molecular Theory What is the Kinetic Molecular Theory of Gases?: This is an explanation of the kinetic motion or molecular motion of the gas molecules. Assumptions that are commonly made Things that are important to remember are: about the model can be: - High temperature = high average kinetic energy of molecule - All particles inside are in constant, - Gases expand to fill their container, but random motion solids and liquids do not - All collisions between particles are perfectly elastic - The volume of the particles in a gas is negligible - The average kinetic energy of the molecules is its kelvin temperature Gas pressure: a measure of the force that a gas exerts on its container (# of collisions) In a lower pressure container, the gas particles are more spread out and do not collide as often as it would in a high pressure container. In a high pressure container, the gas particles are more compacted and are closer together. There are much more collisions in this container than low pressure containers.

Volume, Temperature, and Pressure Information Volume: the 3D space occupied by a solid, liquid, or gas. What units is volume measured in?: Volume is measured in milliliters or liters. It is usually a liquid, so mL and L is the best unit to use. Conversion Methods?: There are lots of ways to convert volume in chemistry, and some of them are: - Going from Liters to Moles: divide the initial volume by the molar volume constant, 22.4 L. - Converting from Moles to Liters: multiply the mole value by the molar volume constant, 22.4 L. - 1 mL= .001 L - 1 L = 1000 mL - 1 cubic meter= 1000 L Temperature: the degree or intensity of heat present in a substance or object. What units is temperature measured in?: Temperature is usually measured in fahrenheit (℉) or celsius (℃). Conversion Methods?: There are different ways that temperature can be converted, and some of these are: - Celsius to Kelvin: ℃ + 273 - Kelvin to Celsius: K - 273 -Celsius to Fahrenheit: ℃ + 32 Pressure: the amount of physical force exerted on an object What units is pressure measured in?: Pressure is measured in Pascal (Pa) which is equivalent to one Newton per square meter (N/m^2). Conversion Methods?: Some of the main conversions for this is: - 1 kPa= 1000 Pa - 101.325 kPa= 10^5 Pa - 1.00 atm= 760.00 mm Hg= 760.00 torr= 29.92 in Hg= 14.7 psi

Ideal Gas Law Statement of the Ideal Gas Law: a description of gas behavior that permits you to solve for the number of moles of a contained gas when given only ONE VALUE EACH for P, V, and T. Which variables are related?: The three variables that are related are pressure (P), temperature (T), and volume (V). Which variables are constant?: the constant variable in the ideal gas law is R. There are other ways that you can solve for something, but the easiest way is to divide the variables before you plug in the the numbers from the problem. Ideal Gas Law Formula: The Ideal Gas Law Formula is PV= nRT

Avogadro’s Principle and Molar Volume What is molar volume: molar volume is the volume that one mole of gas occupies at STP, which is 22.4 Liters STP= standard temperature (273 K or 0℃) and standard pressure (101.3 kPa or 1 atm) Conversion Factors: Avogadro’s Law: the volume of a gas, at a given temperature and pressure, is directly proportional to the quantity of gas Avogadro’s Principle: equal volumes of gases under the same conditions of temperature and pressure contain equal numbers of molecules Important things to know about Avogadro’s Law: - Volume (v) is proportional to to moles (n) - If volume increases, so does the number of moles - Moles and volume are at a constant of temperature and pressure

Boyle’s Law What is Boyle’s Law: Robert Boyle was the “father of chemistry”. He determined that the volume of a confined gas is inversely proportional to the pressure exerted on the gas. *ALL GASES BEHAVE IN THIS MANNER!!* What variables are related?: The variables that are related are volume and pressure. As volume increases, the pressure decreases. What variables are constant?: The constant variables in Boyle’s Law are molecules (n) and temperature (T). What is the formula?: The formula for Boyle’s Law is P1V1 = P2V2 Graphic Representation:

Charles’ Law What is Charles’ Law?: Charles’ Law states that if a given quantity of gas is held at a constant pressure, then its volume is directly proportional to the absolute temperature *MUST USE KELVINS* It is important to use Kelvins because it is used to measure the average kinetic energy. Which variables are related?: Temperature and volume are directly related (directly proportional). Which variables are constant?: The pressure must remain constant if the temperature and volume are directly proportional. What is the formula?: The two formulas that can be used for Charles’ Law are V1 T2 = V2T1 OR V1/T1 = V2/T2. The formula that is the easiest to use is the second one (V1/T1 = V2/T2). Graphic Representation:

Gay-Lussac’s Law What is Gay-Lussac’s Law?: Gay- Lussac’s Law states that volumes of gases always combine with one another in the ratio of small whole numbers, as long as volumes are measured at the same temperature and pressure. Which variables are related?: At constant volume, pressure and temperature of gases are directly related. Which variables are constant?: The constant in Gay-Lussac’s Law is the volume. What is the formula?: The formula for Gay-Lussac’s Law is P1T2 = P2T1 OR P1/T1 = P2/T2. The easiest and most preferred formula to use is the second one (P1/T1 = P2/T2). Graphic Representation:

Combined Gas Law What is the Combined Gas Law?: The Combined Gas Law combines the Laws of Boyle, Charles’, and Gay-Lussac. You can use this law to find the equations for all the other laws. Which variables are related?: The variables that are related in the Combined Gas Law are pressure, temperature, and volume. Which variables are constant?: The constant in the Combined Gas Law is n, which is moles. What is the formula?: The formula for the Combined Gas Law is P1V1/T1N1 = P2V2/T2N2

Practice Problems

Practice Problems Continued