Gas Laws Chapter 11 Section 2

Boyle’s Law Boyle’s law shows the relationship between pressure and volume The relationship is inverse Volume pressure Mathematically: PV = k k is a constant  

Boyle’s Law

Using Boyle’s Law When temperature is held constant: P1V1 = P2V2 P1V1 is the initial pressure and volume P2V2 is the ending pressure and volume

Problem 1 A sample of oxygen gas has a volume of 150.0 mL when its pressure is 0.947 atm. What will the volume of the gas be at a pressure of 0.987 atm if the temperature remains constant? Identify every quantity in the problem with the units

Problem Solution P1 = 0.947 atm V1 = 150.0 mL P2 = 0.987 atm V2 = ? Use Boyle’s law to solve Answer: 144 mL O2 Work problem on page 370

Charles’s Law Charles’s law show the relationship between volume and temperature The relationship is direct Temperature volume V = kT or V/T = k  

Using Charles’s Law When pressure is held constant: V1 and T1 are initial conditions V2 and T2 are ending conditions Temperatures must be in Kelvin to use gas laws (K = °C + 273)

Problem 2 A sample of neon gas occupies a volume of 752 mL at 25°C. What volume will the gas occupy at 50°C if the pressure remains constant? Identify every quantity in the problem with the units

Solution V1 = 752 mL T1 = 25°C + 273 = 298 K T2 = 50°C + 273 = 323 K Use Charles’s law to solve Answer: 815 mL Ne Work both problems on page 372

Gay-Lussac’s Law Gay-Lussac’s law shows the relationship between pressure and temperature The relationship is direct Temperature pressure P = kT or P/T = k  

Using Gay-Lussac’s Law When volume is held constant: P1 and T1 are initial conditions P2 and T2 are ending conditions Temperatures must be in Kelvin to use gas laws (K = °C + 273)

Problem 3 The gas in a container is at a pressure of 3.00 atm at 25°C. Directions on the container warn the user not to keep it in a place where the temperature exceeds 52°C. What would the gas pressure in the container be at 52°C? Identify every quantity in the problem with the units

Solution P1 = 3.00 atm T1 = 25°C + 273 = 298 K T2 = 52°C + 273 = 325 K Use Gay-Lussac’s law to solve Answer: 3.27 atm Work all three problems on page 374

Graphical Representations of the Gas Laws Boyle’s law Charles’s law Gay-Lussac’s law

Combined Gas Law A gas sample frequently undergoes changes in temperature, pressure, and volume all at the same time. The amount of gas remains constant Combined gas law: expresses the relationship between pressure, volume, and temperature of a fixed amount of gas

Combined Gas Law When the amount of the gas is held constant

Problem 4 A helium-filled balloon has a volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at 0.855 atm and 10.0°C? Identify every quantity in the problem with the units

Solution P1 = 1.08 atm T1 = 25°C + 273 = 298 K V1 = 50.0 L Use the combined gas law to solve

Solution 60.0 L He Work both problems on page 375