Ch 11.2 PPT

BELLWORK

ANSWER D

Boyle’s Law

What is Boyle’s Law? Boyle’s Law states that when a gas is under pressure it takes up less space: Boyles Law tells us about the relationship between the volume of a gas and its pressure at a constant temperature. The higher the pressure, the smaller the volume.

VIDEO

Volume vs. Pressure Inverse Relationship

Sample Problem: A deep sea diver is working at a depth where the pressure is 3.0 atmospheres. He is breathing out air bubbles. The volume of each air bubble is 2 cm3. At the surface the pressure is 1 atmosphere. What is the volume of each bubble when it reaches the surface?

BOYLE’S LAW Figure out which variables the problems deals with (Volume and Pressure only) Use the Combined Gas Law Formula (Refer to reference sheet) Ignore the Temperature in the Formula P1V1= P2V2 T1 T2

How we work this out: This is the formula we are going to use: (Derived from the Combined Gas Law on your reference page) Formula first: P1 x V1 = P2 x V2 (Refer to reference Page) Given:= P1 = 3.0 atm V1 = 2 cm3 P2 = 1.0 atm Unknown: V2

Here’s what you should have calculated P1 x V1 = P2 x V2 3 atm x 2 cm3 = 1 atm x V2 6 = 1 (V2) V2= 6 cm3

The Temperature-Volume Relationship Charles’ Law The Temperature-Volume Relationship

Charles’ Law French chemist Jacques Charles discovered that the volume of a gas at constant pressure changes with temperature. Temperature and volume are directly related……As the temperature of the gas increases, so does its volume, and vice versa

VIDEO

Volume vs. Temperature Direct Relationship

Example If the temperature of a given amount of gas is doubled, for example, its volume will also double (as long as pressure remains unchanged).

Charles’ Law Example Problem: 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? Given: V1 = 752 mL T1 = 25°C + 273 = 298K T2 = 50°C + 273 = 323K

Charles’ Law Determine which variables are in the problem. Delete the variable that is not in the problem. (Pressure) That means that pressure remains constant. Use the Combined Gas Law to extrapolate the right equation to solve this problem (reference sheet) P1V1 = P2V2 T1 T2

Equation Used: V1 = V2 T1 T2 752 mL = V2 298 K 323K 298K = 242896mL V2 = 815 mL

Gay-Lussac’s Law

What is Gay-Lussac’s Law? Gay-Lussac’s Law states that when a gas is under constant volume, there is a direct relationship between temperature and pressure. The higher the temperature, the higher the pressure.

Gay-Lussac’s Law: P and T Gay-Lussac’s law states that The pressure exerted by a gas is directly related to the Kelvin temperature. V is constant. An increase in temperature increases the pressure of a gas. 22

PRESSURE VS. TEMP

Calculation with Gay-Lussac’s Law A gas has a pressure at 2.0 atm at 18 ˚C. What is the new pressure when the temperature is increased to 62 ˚C? Which variable is constant? 24

Gay-Lussac’s Law P1 V1 = P2 V2 T1 T2 Used the Combined Gas Law When you have problems that give you volume and pressure. Delete Volume in the Equation P1 V1 = P2 V2 T1 T2

Gay-Lussac’s Law P1 = P2 T1 T2 This formula is used when the volume is constant. P1 = P2 T1 T2

CLASSWORK 11.1 WKSHT