Agenda 4/3/2015 Slip Quiz Part 1 Gas Law Calculations Continued Test Preparation Packet Homework Slip quiz Part 2

Slip Quiz Part 1 Show how you find the answers: 1.What is the equivalent of 50°C in kelvin? 1.What is the equivalent of 50K in degrees Celsius?

Slip Quiz Part 1 Show how you find the answers: 1.What is the equivalent of 50°C in kelvin? K = 50°C = 323°C 2. What is the equivalent of 50K in degrees Celsius? 50K = °C – 273 = -223 °C

Gas Stoichiometry CH 4(g) + 2 O 2(g)  CO 2(g) + 2 H 2 O (g) 1 mole2 moles 1 volume2 volumes1volume2 volumes

CH 4(g) + 2 O 2(g)  CO 2(g) + 2 H 2 O (g) 1 volume2 volumes1volume2 volumes Ex. Qu.: What volume of oxygen gas is needed for the complete combustion of 4.00 L of methane gas? (Assume constant temperature and pressure.) Look at relevant ratios in equation 1 : 2 or 1 volume of CH 4 will need 2 volumes O 2 1L:2L so4L:2L x 4 = 8L Answer: 4 L of methane will require 8.00 L of oxygen for complete combustion.

Ex. Qu. 2: What volume of oxygen gas is needed for the complete combustion of 4.00 L of ethane gas? (Assume constant temperature and pressure.) 2 C 2 H 6(g) + 5 O 2(g)  4 CO 2(g) + 6 H 2 O (g) 2 volumes : 5 volumes 5L Oxygen = xL oxygen 2L ethane 4.00L ethane 5L O LC 2 H 6 = xL oxygen 2LC 2 H 6

Ex. Qu. 2: What volume of oxygen gas is needed for the complete combustion of 4.00 L of ethane gas? (Assume constant temperature and pressure.) 2 C 2 H 6(g) + 5 O 2(g)  4 CO 2(g) + 6 H 2 O (g) 5L Oxygen = xL oxygen 2L ethane 4.00L ethane 5 L O LC 2 H 6 = xL oxygen 2 LC 2 H 6 = 10 L Oxygen

Ex. Qu. 3: What volume of oxygen gas at STP is needed for the complete reaction of g of aluminum in the reaction below: 4 Al (s) + 3 O 2(g)  2 Al 2 O 3(s) 4 moles: 3 moles Look up atomic mass of aluminum amu – remember 1 mole is atomic mass in g So here, 4 moles of Al would be 4 x (26.98g) = g Which is what we are provided with (yeah!)

Ex. Qu. 3: What volume of oxygen gas at STP is needed for the complete reaction of g of aluminum in the reaction below: 4 Al (s) + 3 O 2(g)  2 Al 2 O 3(s) 4 moles: 3 moles g Al needs 3 moles Oxgyen to react completely At STP 1 mole of any gas = 22.4 L 3 moles = 3 x 22.4 L = 67.2 L

Ex. Qu. 3: What volume of oxygen gas at STP is needed for the complete reaction of g of aluminum in the reaction below: 4 Al (s) + 3 O 2(g)  2 Al 2 O 3(s) 4 moles: 3 moles Answer: 67.2 L of oxygen at STP will be needed for complete reaction with g of aluminum. Better - more generally applicable approach gAl x 1mol Al x 3 mol O 2 x 22. 4L = 67.2L O g 4mol Al 1molO 2

24: When iron rusts, it undergoes a reaction with oxygen to form iron(III) oxide as shown in the equation below: 4 Fe (s) + 3 O 2(g)  2 Fe 2 O 3(s) 4 moles: 3 moles Calculate the volume of oxygen gas at STP that is required to completely react with 22.34g of iron. Use better, more generally applicable approach 22.34gFe x 1mol Fe x 3 mol O 2 x 22. 4L = 6.72L O gFe 4mol Fe 1molO 2

24: When iron rusts, it undergoes a reaction with oxygen to form iron(III) oxide as shown in the equation below: 4 Fe (s) + 3 O 2(g)  2 Fe 2 O 3(s) 4 moles: 3 moles 22.34gFe x 1mol Fe x 3 mol O 2 x 22. 4L = 6.72L O gFe 4mol Fe 1molO 2 None of the answers provided are correct. What to do on a test? Show work on paper itself that fully justifies your statement.

AP Bound students: Gas Stoichiometry Practice Problems 60 – 64 (p. 443) 14.4 Mastering Problems (p. 449) 101 – 104

Structured Response Preparation 1.a. The arrow represents the phase transition from solid (graphite) to liquid which is melting.

Structured Response cont. 1b. What is the phase of carbon at a temperature of 1000 K and a pressure of 10 8 Pa? Phase is solid graphite.

Structured Response cont. 1c. How many phases of carbon are represented in the phase diagram and what are they? 4 phases of carbon Diamond(solid) Graphite (solid) Liquid Vapor

More than one possible correct answer. Graphite at a pressure of 10 9 Pa, heat to 2000K and then decrease pressure below 10 7 Pa. Continue to heat graphite past 5000K and then increase pressure of the vapor to the 10 7 Pa required.

Structured Response Preparation 2. Using Dalton’s law of partial pressures Pressure total = Pressure CO2 + Pressure H2O Or PressureCO 2 = Pressure total – PressureH 2 O = kPa – 3.15 kPa = __________kPa

2. b. Collecting carbon dioxide using Displacement of Water ration.htm Why does the collection vessel have to be inverted?

Structured response 3. Differentiate among dispersion forces, dipole-dipole forces, and hydrogen bonds. Dispersion forces are momentary attractions between molecules that occur as a result of temporary shifts in the electron clouds in the molecules which cause temporary dipoles in molecules. All molecules are subject to dispersion forces.

Structured Response 3. cont. Dipole-dipole forces only occur between polar molecules where the molecules have oppositely charged ends as a result of unequal sharing of electrons in covalent bonds as a result of differences in electronegativity of the atoms involved. Dipole-dipole forces can exist for longer than dispersion forces.

Cont. Hydrogen bonds are special dipole-dipole forces that can only be formed when a hydrogen atom is covalently bonded to a small, highly electronegative atom with at least one unbonded pair of electrons on the electronegative atom (O, F or N). Hydrogen bonds result in intermolecular attractions that last for the longest amount of time and have greatest effects on physical properties of materials.

Hydrogen bonding in water Accounts for relatively high melting point, boiling point, properties as a solvent

Multiple choice Preparation 1. A weather balloon with a 1-meter diameter at ambient temperature holds 250 grams of helium. What type of electronic probe could be used to determine the pressure inside the balloon? Cbarometric

2. Which of the following is a monatomic gas at STP? Only Noble gases (Grp 18) are monatomic at STP. Dneon 3. Ammonia gas (NH 3 ) gas diffuses through air because the molecules in air and ammonia are Bmoving randomly.

4. When a cold tire is inflated to a certain pressure and then is warmed up due to friction with the road, the pressure increases. This happens because the Bair molecules speed up and collide with the tire walls more often.

Critical point – after this temperature and pressure gas cannot be liquified

This is triple point – temp. and pressure at which all three phases can coexist

6. Under the same conditions of pressure and temperature, a liquid differs from a gas because the molecules of the liquid Dhave stronger forces of attraction between them.

7. Which molecule below will not undergo hydrogen bonding? Need H, bonded to a highly electronegative, small atom like F, N or O AH 2 O – would hydrogen bond BNH 3 would hydrogen bond C HF would hydrogen bond DXeF 4

8. When someone standing at one end of a large room opens a bottle of lemon juice, it may take several minutes for a person at the other end to smell it. Gas molecules at room temperature move at very high velocities, so what is responsible for the delay in detection of the lemon juice? Crandom collisions between the molecules in air and lemon juice molecules.

9. The random molecular motion of a substance is least when the substance is Ca solid. a gas. – random molecular motion would be greatest in this phase

10. Which of the following is an ionic solid? Metal bonded to nonmetal – most likely candidate Airon – metal, metallic bonding Bpotassium fluoride Cdry ice (solid carbon dioxide) small molecule, covalently bonded Ddiamond - covalent network

11. The volume of 30L of oxygen gas at 30 atm is decreased to 10L at constant temperature. What is the new gas pressure? A90 atm P 1 V 1 = P 2 V 2 at constant T P 1 V 1 = P 2 V 2 30atm30L = P 2 = 90atm 10L

12. Under what circumstance might a gas decrease in volume when heated? DThe gas is placed under increasing pressure.

13. While it is on the ground, a blimp is filled with 6.00 x 10 6 L of helium gas. The pressure inside the grounded blimp, where the temperature is 25 °C, is 1.10 atm. Modern blimps are non-rigid, which means that their volume is changeable. If the pressure inside the blimp remains the same, what will be the volume of the blimp at a height of 2100 m, where the temperature is 15°C? P 1 = 1.10atm V 1 = 6.00 x 10 6 L T 1 = 25°C = 298K P 2 = 1.10atm V 2 = ? T 2 = 15°C = 288K Using combined gas law P 1 V 1 = P 2 V 2 T 1 T 2 V 2 = T 2 P 1 V 1 = 288K1.10atm6.00x10 6 L P 2 T atm298K = 5.79 x 10 6 L

P 1 = 1.10atm V 1 = 6.00 x 10 6 L T 1 = 25°C = 298K P 2 = 1.10atm V 2 = ? T 2 = 15°C = 288K Using combined gas law P 1 V 1 = P 2 V 2 T 1 T 2 V 2 = T 2 P 1 V 1 = 288K1.10atm6.00x10 6 L P 2 T atm298K = 5.79 x 10 6 L

V 2 = T 2 P 1 V 1 = 288K1.10atm6.00x10 6 L P 2 T atm298K = 5.79 x 10 6 L Best choice is A5.80 x 10 6 L

14. Standard temperature and pressure (STP) are defined as C0  C and 1.0 atm pressure 15. Under which of the following sets of conditions will a 4.00 mole sample of helium occupy a volume of 89.6 liters? See question 17, 4 moles of gas at STP will occupy 89.6L, so here the helium must be at STP 0° Cor 273K and 1 atm D273 K and 1.0 atm

16. How many particles will there be in a sample of gas that has a volume of 89.6 L at STP? See 17 below, 89.6L at STP is 4 moles of gas, therefore 4 x 6.02 x particles = x = 2.41 x D2.41 x Calculate the volume that 4 moles of gas at STP will occupy. 4 x 22.4 L = 89.6L A89.6 L

18. A sample of carbon dioxide gas occupies a volume of 10 L at standard temperature and pressure (STP). What will be the volume of a sample of argon gas that has the same number of moles and pressure but twice the absolute temperature? B20 LIf T doubles, then V doubles to keep ratio constant, 2 x 10L = 20 L PV = nRT V = nR T P

19. Theoretically, when an ideal gas in a closed container cools the pressure will drop steadily until the pressure inside is essentially that of a vacuum. At what temperature should this occur? A0 K ABSOLUTE ZERO 20. The temperature at which all molecular motion stops is B0 K Absolute zero

21. What is the equivalent of 100°C in kelvin? K = °C = = 373K C373 K 22. What is the equivalent of 300 kelvin in degrees Celsius? 300K = °C K – 273 = 27°C A27 °C

23. The reaction that provides blowtorches with their intense flame is the combustion of acetlyene (ethyne, C 2 H 2 ) to release carbon dioxide and water vapor. The balanced equation below represents the reaction. 2 C 2 H 2(g) + 5 O 2 (g) → 4 CO 2 (g) + 2 H 2 O (g) Assuming that the pressure and the temperature of the reactants are the same, what volume of oxygen gas is required to completely burn 4.00 L of acetylene?

2C 2 H 2(g) + 5 O 2 (g) → 4 CO 2 (g) + 2 H 2 O (g) B10.00 L 2 L acetylene = 4 L acetlyne 5 L Oxygen xL oxygen XL oxygen = 4L acetlyene 5L Oxygen 2L acetylene X L = 10L

25. Which of the following is an example of an exothermic physical process (one that releases energy into the surroundings)? Aphotosynthesis of glucose - chemical Bwater vapor condensing into liquid water Exothermic physical C combustion of gasoline - chemical Dmelting ice into liquid water – absorbs energy (endothermic)

Homework Review, study, practice – Ch 13 and 14 test preparation. Use notes, use your assessment packet and study guide, use multiple choice questions, use online test questions, flash cards etc. Actively, interactively, thoughtfully study. Just looking over your book or notes is of little use. Test is Tuesday, April 7 th. 25 M/C 2 structured questions.

Slip Quiz Part 2 1.State Avogadro’s principle. 2.What does STP stand for and how is it defined?