Warm Up 4/9 Write the formula of magnesium chloride. Hint: Mg has a charge of +2. Cl has a charge of -1.

Gas Laws

Lesson: Kinetic Molecular Theory

Solids/Liquids/Gases Describe the molecules in the following images.

Kinetic Molecular Theory A model that assumes that an ideal gas is composed of tiny particles (molecules) in constant motion. Ideal Gas- an imaginary gas that perfectly fits all of the KMT.

5 Parts of KMT: 1. Matter is composed of very small particles called molecules. 2. Molecules are in constant motion. The collisions with the walls of the container cause pressure.

Continued 3. When the molecules collide with each other or the walls of a container, there is no loss of energy (elastic collision).

4. There are no forces of attraction or repulsion between gas particles, but they collide and change direction.

5. The average kinetic energy of gas particles depends on the temperature of the gas. Temperature- measure of the average kinetic energy of particles.

Draw a picture for each of the parts of the KMT.

Lesson: Gas Laws (Part 1)

Gas laws express the behaviors of gases as mathematical relationships.

Boyle's Law -Pressure and volume -States that the pressure and volume of a gas are inversely proportional to each other at constant temperature.

Pressure Units Standard atmosphere (atm) 1 atm= 760 mm Hg = 760 torr Pascal- SI unit for measuring pressure: 1 atm= 101300 Pa = 101.3 Kpa

P1*V1 = P2*V2 Boyle's Law Formula: P1= initial Pressure P2= final pressure V1= initial volume V2= final volume

Boyle’s Law Example‏ A gas has a volume of 1.25 L and a pressure of 755 torr. What will the new volume be if the pressure is increased to 2667.6 torr?

Charles' Law -Volume and temperature -The volume of a gas is directly proportional to the temperature at constant pressure.

Charles' Law Formula: **Temperature must be in Kelvin! V1= initial volume V2= final volume T1= initial temperature T2= final temperature **Temperature must be in Kelvin!

Charles’s Law Example 1‏ If a gas has a volume of 247 mL at 25.0°C, what will the new volume be if the temperature is increased to 308°C?

Charles’s Law Example 2‏ If a gas has a volume of 247 mL at 25.0°C, what will the new temperature be if the volume is increased to 255 mL?

Practice Problems Boyle’s Charles’ 1. A gas occupies 12.3 liters at a pressure of 40.0 mm Hg. What is the volume when the pressure is increased to 60.0 mm Hg? 2. A gas occupies 11.2 liters at 0.860 atm. What is the pressure if the volume rises to15.0 L? Charles’ 3. 600.0 mL of air is at 20.0°C. What is the volume at 60.0 °C? 4. If 15.0 liters of neon at 25.0 °C is allowed to expand to 45.0 liters, what will the new temperature be?

Ideal Gas Law Formula: PV = nRT n = number of moles R = universal gas constant (.0821) T = temperature (Kelvin) P= pressure (in atm) V = volume (in Liters)

Universal Gas Constant (R)‏ -value can vary depending on pressure units being used.

Example #1 (Ideal Gas Law)‏ What is the pressure of 5 moles of a gas at 30°C in a 2 liter container? P x 2 L = 5 mols x 0.0821 x 303 K 2 L 2 L P = 60 atm

Example #2 (Ideal Gas Law)‏ A 250 mL of a gas exerts a pressure of 760 torr at 10°C. How many moles of gas are present? 1 atm x 0.250 L = n x 0.0821 x 283 K (0.0821 x 283 K) 0.0821 x 283 K n = 0.0108 mol

Lesson: Gas Laws (Part 2)

Dalton's Law of Partial Pressures -states that the pressure of a gas mixture is the sum of the partial pressures of the gases in the mixture.. Formula: Ptotal = P1+P2+P3+...

Example (Partial Pressure)‏ A mixture of oxygen, hydrogen and nitrogen gases exerts a total pressure of 278 kPa. If the partial pressures of the oxygen and the hydrogen are 112 kPa and 101 kPa respectively, what would be the partial pressure exerted by the nitrogen? 278 – 112 – 101 = 65 kPa

Avogadro’s Law -Volume and number of moles -States that the volume and # of moles of a gas are directly proportional to each other at constant temperature and pressure.

Avogadro’s Law Also means: Equal volumes of 2 gases at the same temperature and pressure have equal numbers of moles. STP = Standard Temperature and Pressure (0°C, 1 atm) 1 mole of gas = 22.4 L at STP

Avogadro‘s Law Formula: V1= initial volume V2= final volume n1= initial # of moles n2= final # of moles

Moles: 0.214 Moles: 0.375 Volume: 652 mL Volume: ? Example 652 mL V = 652 x .375 / .214 = 1142 mL

Left Side Practice 1. If a mixture of oxygen gas and water vapor have a total pressure of 754 torr, and the water vapor has a partial pressure of 21 torr, what is the partial pressure of the oxygen? Moles: 9.6 Moles: 6.8 Volume: 100.0 L Volume: ? 3. If 2.00 mol of gas occupies 4.50L at STP. How much of the same gas will occupy 3.00L at STP? 4. A propane tank containing 55L has 2.46 moles of the gas. (C3H8 is propane!) What would be the number of moles if ½ of the gas is used?