Chemistry H handouts

Recent Handouts Chapter 4 pretest Reaction types examples Chapter 5 pretest pretest answers

Annoucements

Chapter 5

The Chapter 5 pretest is now up. Should be similar in length to the chapter 5 test. Download and attempt the problems early in the chapter.

Webassign for chapter 5 is up. There is an extra credit WebAssign for gas laws. All written work for this assignment must be submitted.

Please look at chapter four on the Chang Online Learning Center. Go through the Essential Study Partner partial pressures at some point before returning from Thanksgiving.

Upcoming Asssignments

Monday (pg. 193 # 5.17-5.19) answers

Due Tuesday (pg. 194 # 5.21, 5.22, 5.23, 5.24) answers

Due Monday (# 5.29 - 5.32) answers

Due Monday (# 5.44 - 5.47) answers

Due Tuesday (# 5.53, 5.85, 5.93) answers

Due Friday (5.58 - 5.61) answers

Due Monday. Do the following problems.

1. How many time faster than oxygen does helium effuse?
2. V L of a sample of gas at 273 K and pressure P is reduced in volume to 0.1 V L at constant temperature.

• How does this affect the pressure
• How does this affect the number of collisions of the molecules with the walls of the container?
• How does this affect the average molecular speed?

3. An unknow gas diffuses at the rate of 16 mL/s. In the same apparatus, nitrogen diffused at the rate of 24.2 mL/s. What is the molecular weight of the first gas?

Retroproblem: If 27.6 mL of a 0.40 M barium hydroxide solution was required to titrate 20.0 mL of a hydrochloric acid solution to its endpoint.

• What type of reaction is this?
• Write a balanced equation including state symbols.
• Write a net ionic equation for the reaction.
• What is the concentration of the acid?

Remember:

760 torr = 1 atm = 101.3 kPa

Boyles Law (Constant Temperature)

• Pressure is inversely related to Volume
• Know the shape of a P vs V curve
• P₁V₁ = P₂V₂
• See a Boyles law mixing problem

Charles Law (Constant Pressure)

• Pressure is directly proportional to absolute temperature. P = kT
• Constant P
• T must be in Kelvin
• K = (deg C) + 273

Combined Gas Law

• Constant number of moles . SEE PROBLEMS 5.37, 5.38 and 5.39.
• T in Kelvin

Avogadro's Law

• mole ratios in a balanced chemical equation are liter ratios. Why?
• Because one mole of any gas occupies the same volume at the same temperature and pressure.
• 1 mole gas = 22.4 L at STP
• STP: T = 273 K, P = 1 atm

Ideal Gas Law

• PV = nRT (R depends on Pressure units!!!)
• R = Ideal Gas Constant
• R = 0.0821 L atm/mol K
• R = 8.31 L kPa/mol K
• R = 62.4 L mmHg/mol K

Gas Stoichiometry

• Treat it as a normal stoichiometry
• For gases at the same temperature and pressure, mol ratios are liter ratios
• If conditions are STP, then 1 mol gas = 22.4 L
• If not use PV = nRT

Daltons Law of partial pressures

• P_tot = P_a + P_b + ... Basically, the total pressure in a container is the sum of the partial pressures
• Pa = x_a(P_tot) (partial pressure of gas a is the mol fraction of a times total pressure)
• x_a = mol of gas a/total number of moles
• An important time to use the law of partial pressures is when a gas is collected over water. When this is the case, the gas collected is a mixture of some product gas and some water vapor. P_tot = P_product + P_water

Useful Links

Ohio State University Gas Law Video Lessons

Interactive Ideal Gas Law Simulation (you set the variables and see how the others change)