Gas Laws Ch 13
FTF Day 9 April 9, 2012 HW: Assessment Questions 13.1 (Wed) Folder Check Quiz on Wednesday Topic: Gas laws Question: What are gasses like? Describe motion of particles, compressibility, density, types of gasses, etc.
Activities Check Ch 12 quiz Discuss properties of gasses
Brainstorm kinds of gasses
Kinds of gasses Air: oxygen O 2 nitrogen N 2 ozone O 3 argon Ar carbon dioxide CO 2 water H 2 O Noble gases: helium He neon Ne krypton Kr xenon Xe Other gases: fluorine F 2 chlorine Cl 2 ammonia NH 3 methane CH 4 carbon monoxide CO nitrogen dioxide NO 2 sulfur dioxide SO 2
Kinetic energy in gasses How do particles move in a solid, liquid, or gas? http://phet.colorado.edu/en/simulation/states-ofmatter-basics
FTF Day 10 April 10, 2012 HW: 13.1 + 14.1 assessment questions Topic: Properties of gasses Questions: Here s a riddle! There is a truck stuck under a bridge and no one can figure out how to free the truck. Along comes a chemist who knows her stuff and frees the truck in 2 minutes. No further damage to the truck is done. How d she do it?
There is a truck stuck under a bridge and no one can figure out how to free the truck. Along comes a chemist who knows her stuff. She frees the truck in 2 minutes with no further damage to the truck is done. How d she do it?
What can we answer by knowing the gas laws? What makes a balloon hold its shape? Why does a hot air balloon rise? Why does it rain? Why do mountain climbers have a difficult time breathing? How can I smell that fart from all the way over here when he s all the way over there?? Why does a Dust-Off can or a barbeque gas tank have a warning against frost bite? Why did that soda explode when I left it in the car? What is The Benz and why is it so dangerous? How can I make water boil at room temperature? How do planes fly? How do birds fly? Do they use the same technique? And more
Factors that affect gasses Factor Variable you will see in the gas laws Units used to measure this factor Temperature Pressure Volume Number of particles
Factors that affect gasses Factor Variable you will see in the gas laws Units used to measure this factor Temperature T Kelvins (K) Celsius C Pressure P atm - Atmospheres mm Hg milligrams of Hg Pa or kpa pascals Volume V L Liters dm 3 decimeters cubed Number of particles n Mol- Moles
What is pressure? Pressure is the result of simultaneous collisions of billions of rapidly moving particles of gas with an object. Barometer Measures atmospheric pressure http://phet.colorado.edu/en/simulation/states-of-matter-basics
Barometers
FTF Day 11 April 11, 2012 HW: 13.1 and 14.1 Assessment questions is due tomorrow, yall Topic: properties of gasses, combined gas law. Questions: Convert the following values 32 atm = mm hg 1400 mm Hg = kpa (1 atm = 760 mm Hg = 101.3 kpa)
Activities Combined Gas Law Practice Problems Can Crush
If you change one variable, how does it affect the others? Temperature Pressure Volume Number of particles
Boyles Law http://www.kentchemistry.com/links/gaslaws/boyles.htm
Charles Law http://www.kentchemistry.com/links/gaslaws/charles.htm
http://www.kentchemistry.com/li nks/gaslaws/gaylussac.htm Gay-Lussacs Law
Combined Gas Law P 1 V 1 = P 2 V 2 T 1 T 2 BEFORE AFTER LecturePLUS Timberlake 20
Combined Gas Law P 1 V 1 = P 2 V 2 T 1 T 2 Rearrange the combined gas law to solve for V 2 P 1 V 1 T 2 = P 2 V 2 T 1 V 2 = P 1 V 1 T 2 P 2 T 1 LecturePLUS Timberlake 21
Learning Check C1 Solve the combined gas laws for T 2. Write the answer in your notes AND on the white board. LecturePLUS Timberlake 22
Solution C1 Solve the combined gas law for T 2. (Hint: cross-multiply first.) P 1 V 1 = P 2 V 2 T 1 T 2 P 1 V 1 T 2 = P 2 V 2 T 1 T 2 = P 2 V 2 T 1 P 1 V 1 LecturePLUS Timberlake 23
Combined Gas Law Problem A sample of helium gas has a volume of 0.180 L, a pressure of 0.800 atm and a temperature of 203 K. What is the new temperature of the gas at a volume of 90.0 ml and a pressure of 3.20 atm? What is the new temperature in Celsius? LecturePLUS Timberlake 24
Data Table Set up Data Table P 1 = 0.800 atm V 1 = 0.180 L T 1 = 302 K P 2 = 3.20 atm V 2 = 90.0 ml T 2 =???? LecturePLUS Timberlake 25
Solution Solve for T 2 Enter data T 2 = 302 K x atm x ml = K atm ml T 2 = K - 273 = C LecturePLUS Timberlake 26
Calculation Solve for T 2 T 2 = 302 K x 3.20 atm x 90.0 ml = 604 K 0.800 atm 180.0 ml T 2 = 604 K - 273 = 331 C LecturePLUS Timberlake 27
Learning Check C2 A gas has a volume of 675 ml at 35 C and 0.850 atm pressure. What is the temperature in C when the gas has a volume of 0.315 L and a pressure of 802 mm Hg? LecturePLUS Timberlake 28
Solution G9 T 1 = 308 K T 2 =? V 1 = 675 ml V 2 = 0.315 L = 315 ml P 1 = 0.850 atm P 2 = 802 mm Hg = 646 mm Hg T 2 = 308 K x 802 mm Hg x 315 ml 646 mm Hg 675 ml = 178 K - 273 = - 95 C LecturePLUS Timberlake 29
Learning Check C3 True or False 1. The P exerted by a gas at constant V is not affected by the T of the gas. 2. At constant P, the V of a gas is directly proportional to the absolute T 3. At constant T, doubling the P will cause the V of the gas sample to decrease to one-half its original V. LecturePLUS Timberlake 30
Solution C3 True or False 1. False The P exerted by a gas at constant V is not affected by the T of the gas. 2. True At constant P, the V of a gas is directly proportional to the absolute T 3. True At constant T, doubling the P will cause the V of the gas sample to decrease to one-half its original V. LecturePLUS Timberlake 31
FTF Day 1 Monday April 16, 2012 HW: Gas Laws Packet Due tomorrow Topic: Combined Gas Law Question: none
FTF Day 2 April 17, 2012 HW: Bring Tissue Paper to class as soon as possible. Topic: Ideal gas law Questions:
Ideal Gas Law The equality for the four variables involved in Boyle s Law, Charles Law, Gay-Lussac s Law and Avogadro s law can be written P = Pressure V = Volume PV = nrt n = number of moles R = ideal gas constant T = Temperature Lecture PLUS Timberlake 2000 34
Ideal Gases Behave as described by the ideal gas equation; no real gas is actually ideal Within a few %, ideal gas equation describes most real gases at room temperature and pressures of 1 atm or less In real gases, particles attract each other reducing the pressure Real gases behave more like ideal gases as pressure approaches zero. Lecture PLUS Timberlake 2000 35
PV = nrt R is known as the universal gas constant Using STP conditions P V R = PV = (1.00 atm)(22.4 L) nt (1mol) (273K) n T = 0.0821 L-atm mol-k Lecture PLUS Timberlake 2000 36
Solution G15 What is the value of R when the STP value for P is 760 mmhg? R = PV = (760 mm Hg) (22.4 L) nt (1mol) (273K) = 62.4 L-mm Hg mol-k Lecture PLUS Timberlake 2000 37
R Values R = 0.0821 L-atm mol-k R = 62.4 L-mm Hg mol-k R = 8.31 kpa dm 3 mol - K Lecture PLUS Timberlake 2000 38
Learning Check G16 Dinitrogen monoxide (N 2 O), laughing gas, is used by dentists as an anesthetic. If 2.86 mol of gas occupies a 20.0 L tank at 23 C, what is the pressure (mmhg) in the tank in the dentist office? Lecture PLUS Timberlake 2000 39
Solution G16 Set up data for 3 of the 4 gas variables Adjust to match the units of R V = 20.0 L T = 23 C + 273 20.0 L 296 K n = 2.86 mol 2.86 mol P =?? Lecture PLUS Timberlake 2000 40
Rearrange ideal gas law for unknown P P = nrt V Substitute values of n, R, T and V and solve for P P = (2.86 mol) (62.4L-mmHg) (296 K) (20.0 L) (K-mol) = 2.64 x 10 3 mm Hg Lecture PLUS Timberlake 2000 41
Learning Check G17 A 5.0 L cylinder contains oxygen gas at 20.0 C and 735 mm Hg. How many grams of oxygen are in the cylinder? Lecture PLUS Timberlake 2000 42
Solution G17 Solve ideal gas equation for n (moles) n = PV RT = (735 mmhg)(5.0 L)(mol K) (62.4 mmhg L)(293 K) = 0. 20 mol O 2 x 32.0 g O 2 = 6.4 g O 2 1 mol O 2 Lecture PLUS Timberlake 2000 43
Practice problems 14.3 Assessment questions pg 426
Chem: FTF Day 3 April 20, 2012 HW: Balloon Fly Day is on Monday Topic: gas laws Question: What are the conditions (pressure and temperature) of a gas at STP? What is the volume of 2 moles of gas at STP? If I initially have a gas at a pressure of 2 atm at 10 C and I double the pressure, what will be the new temperature of the gas?