Warm-Up 12/9/2016 Which represents the formula for Iron (III) Chromate? A) Fe2(CrO4)3 B) Fe2(CrO4)2 C) Fe3(CrO4)2 D) Fe3(CrO4)3

Unit 5 Gas Laws and Kinetic Molecular Theory

Kinetic Molecular Theory(K.M.T) The Kinetic Molecular Theory is used to describe the behavior of gases The Theory describes the motion of the particles of a gas

Assumptions of the Kinetic Molecular Theory 1. Gases consist of large numbers of tiny particles 2. These particles are in rapid motion they possess kinetic energy (energy of motion)

Assumptions Continued 3. All collisions the particles make between any substance are perfectly elastic collisions Elastic Collisions is one in which there is not net loss of kinetic energy 4. The particles do NOT interact with each other In other words, the particles do not attract or repel each other

Important Terms in Describing Gases Devices Used to Measure Pressure: 1. Barometers-which is an instrument that is used to measure atmospheric pressure 2. Manometers-is an device employed to measure pressure inside of a container

Important Terms in Describing Gases Gas Pressure: results from the numerous collisions of particles [Pressure is equal to force divided by area] P=F/A When no particles are present, no collisions occur which creates a VACUUM

The following are possible units used for pressure: Pascal [Pa] Units for pressure The following are possible units used for pressure: Pascal [Pa] kiloPascal [kPa] millimeter of mercury [mm Hg] torr [torr] atmosphere [atm]

Conversions Involving Volume The official SI unit for volume is the kPa Conversions Factors: 1 kPa = 1000 Pa 1 atm = 101.3 kPa 1 atm = 760 mm Hg 1 atm = 760 torr

Example Problems 1. How many atm are in 600 kPa? 2. How many mm Hg are in 505.6 kPa?

Factors that Affect Gases Four factors affect gases: 1. Pressure 2. Temperature 3. Amount of Substance Present (mole) 4. Volume

How is Pressure effect Gases? Adding more gas increases the pressure Decreasing the volume that the gas occupies increases pressure

Temperature Temperature is a measure of the average kinetic energy of particles of an object Possible Temperature Units: Celsius and Kelvin K = 273 + °C

Values for STP are 1 atm pressure and 0 °C Other Important Terms Absolute Zero: as temperatures begin to approach this value, the motion of the particles slow down to a standstill This value is -273 °C or 0 K Standard Temperature and Pressure (STP): standard measurements used by scientists Values for STP are 1 atm pressure and 0 °C

Temperature and Volume For an increase in temperature, heat or energy must be added When energy is added, the particles absorb the energy and begin moving more quickly Therefore the particles spread out producing an increase in volume

Temperature and Volume Temperature and Volume are directly related Directly means that as one variable changes, the other variable changes in the same direction

Volume Units for Volume: m3, cm3, dm3, mL, L Relationships: 1 mL = 1 cm3 1 dm3 = 1 L

Combined Gas Law Charles and Boyle’s Laws can be combined together to yield a combined gas law The Combined Gas Law allows for changes in volume, temperature, and pressure

Combined Gas Law P1 * V1 T1 T2 P2 * V2 =

Variables in Combined Gas Laws V1 = original volume P1 = original pressure T1 = original temperature (in K) V2 = final volume P2 = final pressure T2 = final temperature (in K)

Example Problem #1 A helium balloon has a volume of 50.0 L at 25 ° C and 820 mm Hg. What volume will it occupy at 650 mm Hg and 10°C? Ans) 59.9 L

Example Problem #2 The volume of a gas is 27.5 mL at 22°C and 740 mm Hg pressure. What will be its volume at 15°C and 755 mm Hg? Ans) 26.3 mL

Practice Problem # 3 A gas occupies a volume of 34.5 cm3 at 345 torr and 45ºC. What is the new pressure if the gas expands to a volume of 56.8 mL and temperature of 34ºC? Answer = 202.3 torr

Practice A balloon indoors, where the temperature is 27° C, has a volume of 2.00 L. What will its volume be outdoors, where the temperature is -23°C?

Practice Question If you were able to take a volleyball scuba diving with you, what would be its new volume if it started at the surface with a volume of 2.00 L, under a pressure of 752.0 mmHg and a temperature of 20.0 ˚C ? On your dive you take it to a place where the pressure is 2943 mm Hg, and the temperature is 2.45 ˚C.