11/22

review yesterday: When reaction occurs, the pressure changes to create equilibrium with the atmosphere.


Regular buildings don't affect atmospheric pressure.

We talked about laws of gases and changes in pressure that are regulated in certain buildings or underground caves and how pressure differences can be used to contain viruses in the CDC building.

Stoichiometry:

Volume of a gas under 2 sets of conditions, non-standard temperature and non standard pressure

Here are some examples, these problems can be found in the Unit 5 handouts folder, here’s how to set up the equations if you don’t understand it.

Ammonia is NH3, our “B” chemical, 6NO is our “A” chemical, however there is a typo in the question, there is no indication of pressure or temperature, so we assume STP and -273 degrees kelvin.

Start by writing 12 L NO, turn it into moles by using volume, 1 mol NO/ 22.4L NO.

12 L NO x(1 mol NO/22.4 L NO) x (4 mol NH3/6 mol NO) x (22.4 L NH3/1 mol NH3)

12 x 4 / 6 = 8 L NH3

102 g H2S x (1 mol/34.09 g H2S) x (3 mol O2/2 mol H2S) x (22.4 L O2/1 mol O2) =

100.5 ->101 L O2

12 g H2O2 x (1 mol H2O2 / 34.02 g H2O2) x (1 Mol O2 / 2mol H2O2) = 0.18 mol O2 -> PV=nRT

746 mmHg x V = 0.10 mol O2 x 62.4 (Lx mmHg/mol x K) x 300 K

V= 4.5 L

REMEMBER: You can treat volume like moles when its at standard pressure.

At the end of class today we did a demo about pressure how marshmallow and shaving cream expand in in volume when pressure is decreased and shrivel when pressure increases.

DONT FORGET TO DO YOUR PACKET THIS WEEKEND AND STUDY

Class Blog 10/16/13

Chem Blog 10-16-13

What we did:

--Checked in Homework (Two stoich worksheets + Pre-lab)

--Went over homework (Keys are posted on moodle)

--We were assigned partners, exchanged phone numbers, and were assigned a take-home quiz that we will do with our partners tonight

--Did the Copper and Silver Nitrate lab

Lab Data:

SIlver Nitrate: 1.44g

Copper Wire: 0.73g

Mass of 100 mL beaker: 50.15g

Final Mass: 0.72g

Change of Copper Weight: 0.01g

Homework:

1) You have been assigned a partner to work with to complete Stoich Quiz #2 for homework (posted in the Unit 2 Handouts folder).  If you cannot meet with your partner in person, call them and do the quiz via phone meeting; you should have exchanged phone numbers in class today.  Plan on taking about 15 minutes together.  Follow the directions on the quiz and work as "expert" and "editor".  Due tomorrow.

2) The "Copper and Silver Nitrate" prelab was due in class today.  Check your answers against the key that is posted in the Unit 3 Keys folder.  THEN write 1-2 sentences in your journal that summarize what we are trying to accomplish with this lab.  WHAT ARE WE GOING TO CALCULATE WITH OUR LAB DATA?  Due tomorrow.

3) The "Copper and Solver Nitrate" lab write-up will be due on Monday, October 21.  If you were absent today, get data from the blog post and use that to complete the write-up.

4) Just a heads-up -- our unit 3 test is one week from today, next Wednesday, 10/23.

Next Blogger: Carrie Reusche

Class Blog 10/14/13

Class Notes 10/14/13

1. Homework was checked in, which was taking notes on stoichiometry video.

2. Beginning of class was spent briefly reviewing the quizzes we took on Friday

-Remember it’s ok to sometimes fail!

3. 4 Stoichiometry worksheets were passed out. (Examples were done on 2 of them)

4. Next, we took an introduction to Stoichiometry, which is similar  to earlier molar mass conversions done earlier, only these go more in depth.  

-Ms. Friedmann’s in-class notes can be found here on Moodle.

-Stoichiometry is used to compare two “things” (thing 1 and thing 2). Usually, you are given

thing 1 and have to find thing 2

.

-We use mass and mole conversions to help us achieve this.

-Remember the conversion factor:

Mass (grams to molar mass) * Moles (Molar mass to particles) * Avogadro’s Number

Homework:

“1) Complete the Intro to Stoichiometry Wss (worksheets) posted in the Unit 3 Handouts folder.  Due tomorrow.  If you were absent today, take a look at the examples done and refer to the Intro Notes on Stoichiometry (posted in the Unit 3 Notes folder) and see if that's enough to help you get started.

2) Go to the blog and contribute to the class effort to solve the problem I posted there today.  Everyone must make a constructive comment that shows your attempt to process the problem.  The goal is for everyone to understand how to solve this problem by the time we meet in class tomorrow.  WE ARE NOT DONE WHEN THE CORRECT ANSWER IS POSTED; WE ARE DONE WHEN EVERYONE UNDERSTANDS HOW THE CORRECT ANSWER WAS ACHIEVED. “

Next Blogger: Dorothy Wasilewski