C. Units: volume can be in any units, typically we will use L or mL. refers to the number of moles it can refer “n” – to the number of particles but not grams! D. Example A balloon with a volume of 4.00 L is to contain 0.200 moles of gas. How many moles of gas – remain if some of the gas is released and the new volume is 3.25 L. Assume temperature and pressure remain constant. V. The Combined Gas Law Boyle’s, Charles’, and Gay-Lussac’s Laws and Avagadro’s combined. – A. Formula: B. Units any units for volume and pressure can be used as long as you are consistent, BUT YOUR TEMPERATURE – MUST BE IN KELVIN! D. Examples: Show all work including units. 1. A sample of gas has a volume of 1.25 L at 25°C and 0.876 atm. What is the new volume when the temperature decreases to 15°C and the pressure decreases to 0.750 atm? 2. A sample of gas occupies 15.0 L at 22.°C and 754 mm Hg. If the volume increases to 23.0 L and the pressure decreases to 723 mm Hg, what is the new temperature? Ideal Gas Law Ideal Gas Law gives the relationship between the pressure, volume, temperature, and number of moles for a sample of gas. The – Ideal Gas Law is derived from the Combined Gas Law Assume that you have 1.00 mole of gas at STP. Then P1 = 1.00 atm, T1 = 273 K, n1 = 1.00 mole, and V1 = 22.4 L. Plugging these values into the equation above we get: Since the standard conditions are called constants, we can create a new constant combining all of them. This constant is called the ideal gas constant and is given the symbol R. Using the ideal gas constant, R, we can derive another gas law, the IDEAL GAS LAW which usually expressed as follows: PV = nRT P = pressure in atmospheres V = volume in Liters n = the amount of substance in moles T = the temperature in Kelvin
C. Units: volume can be in any units, typically we will use L or mL. “n” refers to the number of moles – it can refer to the number of particles but not grams! D. Example – A balloon with a volume of 4.00 L is to contain 0.200 moles of gas. How many moles of gas remain if some of the gas is released and the new volume is 3.25 L. Assume temperature and pressure remain constant. V. The Combined Gas Law – Boyle’s, Charles’, and Gay-Lussac’s Laws and Avagadro’s combined. A. Formula: B. Units – any units for volume and pressure can be used as long as you are consistent, BUT YOUR TEMPERATURE MUST BE IN KELVIN! D. Examples: Show all work including units. 1. A sample of gas has a volume of 1.25 L at 25°C and 0.876 atm. What is the new volume when the temperature decreases to 15°C and the pressure decreases to 0.750 atm? 2. A sample of gas occupies 15.0 L at 22.°C and 754 mm Hg. If the volume increases to 23.0 L and the pressure decreases to 723 mm Hg, what is the new temperature? Ideal Gas Law Ideal Gas Law – gives the relationship between the pressure, volume, temperature, and number of moles for a sample of gas. The Ideal Gas Law is derived from the Combined Gas Law Assume that you have 1.00 mole of gas at STP. Then P1 = 1.00 atm, T1 = 273 K, n1 = 1.00 mole, and V1 = 22.4 L. Plugging these values into the equation above we get: Since the standard conditions are called constants, we can create a new constant combining all of them. This constant is called the ideal gas constant and is given the symbol R. Using the ideal gas constant, R, we can derive another gas law, the IDEAL GAS LAW which usually expressed as follows: PV = nRT P = pressure in atmospheres V = volume in Liters n = the amount of substance in moles T = the temperature in Kelvin
unit_10_-_gases.docx