Catalyst L of an unknown gas has a mass of 10.8 grams at a temperature of 310 K and 1.2 atm. What is the molar mass of this mass? What is the identity of the gas?

Loose Ends Labs and Lab Write – Ups The only way you learn from labs is through the analysis These are not meant to torture. They honestly help with the content. E.g. Net Ionic Equation Lab Lab Reports Human Error – Don’t want to see it ever again in a report…you can’t BS a teacher that made it through education using the same BS. Plagiarism New Lab Report/Write-Up Policy You call mom/dad/guardian to explain why your don’t value your education No lab write up = No lunch/nutrition You will do the write up during lunch/nutrition, but you will not get the points

J – TPS If the atmosphere at 120,000 ft contained oxygen, nitrogen, and hydrogen at pressures of atm, atm, and atm, then what is the pressure of the atmosphere at this height?

Lecture 4.2 – Partial Pressures and Deviations from Ideality

Today’s Learning Targets LT 4.4 – I can discuss Dalton’s Law of Partial Pressures. Additionally, I can calculate partial pressures for a gas mixture LT 4.7 – I can compare and contrast ideal and real gases. I can discuss how the Van der Walls equation corrects for these deviations from ideality.

Dalton’s Law of Partial Pressures The total pressure of a mixture of gases equals the sum of all the partial pressures This means that we can add up all the individual pressures (partial pressures) to get the overall pressure of a system.

Class Example A mixture of 6.00 g O 2 (g) and 9.00 g CH 4 (g) is placed in a 15.0 L vessel at 0 o C. What is the partial pressure of each gas, and what is the total pressure in the vessel?

Table Talk What is the total pressure exerted by a mixture of 2.00 g of H 2 and 8.00 g of N 2 at 273 K in a 10.0 L vessel.

Mole Fractions Because each gas acts independently even when mixed, we can relate the amount of moles of gas in a mixture. The mole fraction (X) expresses the ratio of moles of gas to total moles of gas in the system

Class Example A study of the effects of certain gases on plant growth requires a synthetic atmosphere composed of 1.5 mol percent CO 2, 18.0 mol percent O 2, and 80.5 mol percent Ar. Calculate the partial pressure of O 2 in the mixture if the total pressure of the atmosphere is to be 745 torr.

Table Talk The composition of the atmosphere of Saturn’s moon Titan has been estimated. The pressure on the surface of Titan is 1220 torr. The atmosphere consists of 82 mol percent N 2, 12 mol percent Ar, and and 6.0 mol percent CH 4. Calculate the partial pressure of each gas.

Collecting Gas Over Water In most labs, we bubble gas through water and catch it in some vessel. This is known as collecting a gas over water We must correct for the pressure of the water vapor that is present in the air above where the gas was collected

Class Example When a sample of KClO 3 is partially decomposed, O 2 is produced and the gas is collected over water. The volume of the gas collected is L at 26 o C and 765 torr. How many moles of O 2 are collected? NOTE – At 26 o C, the P H2O is 25 torr.

Table Talk Ammonium nitrate decomposes on heating to form N 2 gas: NH 4 NO 2 (s)  N 2 (g) + 2H 2 O (l) When a sample of NH 4 NO 2 is decomposed

Collaborative Poster In a group of three, analyze and solve the problems given to you. Assign person A, B, and C in your group Person A – Identify the values for all variables and givens in the problem Person B – Identify and write the equations that you will need to use to solve these problems Person C – Solve the problem.

1. 2 I - + Pb 2+  PbI 2 2. Cs 2 O + H 2 O  2CsOH 3. 2 H + + ZnS  H 2 S + Zn 2+

Lab 8 – Molar Mass of Butane Gas

Lab Work Time

Work Time For the remainder of class, please begin your homework that will be due Thursday/Friday

Closing Time Read 10.6 and answer essential questions on reading guide Complete book questions: 10.63, 10.65, 10.66, 10.69, 10.71, 10.73, and 10.74