Just a friendly reminder that your Limiting Reactant Packet is due by the end of the period on Friday and your test is

Next Tuesday March 5th

Today we’ll be finishing Handout #2 (Which you should have started yesterday). You will have a quiz tomorrow… and it is currently posted on the Docs page and below this clever sign. Have a Happy Valentines Day!

Stoichiometry Quiz

Mr. Fogel and I have decided to move our “Quest” back to Tuesday to give our students more of an opportunity to practice our atom-mole-molecule problems and see the set up of the test.

We’ll continue working on our atom-mole-molecule calculations today. The goal is to have this done by Thursday to have time to prep for the “quest” on Friday. (It’s bigger than a quiz, but smaller than a test… it’s a quest, get it?)

These calculations can take time to do so be patient and be persistent. Check your work on the Semester 1 Docs page!

We’ll be continuing our use of the Mole this week by using it to do calculations with entire molecules, not just atoms. So, we’ll be adding a whole new side to the chart that we started last week. See below.

If you’re struggling to remember how to calculate Molar Masses, search for the post on “molar mass” on this site. We’ll have a quiz over moles on Thursday and knowing how to use this chart to find the units you are looking for will be very helpful. There is also a homework assignment tonight (Grams to Moles to Molecules) which can be found on the “Docs” page. If you’re struggling with the calculations, watch the Voicethread.

Lets say you have 2.5 moles of Au (Gold) and you’re really curious as to how many atoms of gold are in that sample. What should we do? Well just remember what Chemistry Cat says about MOLE PROBLEMS:

For any element or compound, 1 mole is equal to Avogadro’s Number of particles of that element or compound.

1 mole = 6.022 x 10²³

So, lets start plugging into a factor label equation the same way we did for Moles to Grams equations.

2.5 mole Au atoms   ->   __________  Au atoms

Since 1 mole is equal to Avogadro’s number, we can put that into our formula as…

6.022 x 10²³ Au atoms
1 mole Au atoms

So lets put this value into our formula and see if we can make this work…

2.5 mole Au atoms   x   6.022 x 10²³ Au atoms
1                                      1 mole Au atoms

We can cross out the “mole Au atoms” units so the only unit remaining is “Au atoms“. So…

2.5 x 6.022 x 10²³ Au atoms       =       1.506 x 10²⁴ Au atoms

___________Easy! When you go from grams to moles you MULTIPLY BY THE ATOMS!_______________
But, what if I want to go from atoms to moles??? EASY!!! DIVIDE BY AVOGADRO’S NUMBER!
How many moles of Zn is 2.75 x 10²⁴ atoms of Zn?

2.75 x 10²⁴ Zn atoms   x   1 mole Zn atoms            =  4.57 mole Zn atoms
1                                      6.022 x 10²³ Zn atoms

Since, 1 mole of any element = Avogadro’s number of atoms (or molecules), you can flip the equation to work for you! Since we have moles on the top left of the formula, we want moles on the bottom right so they can cancel out!

Your homework for tonight is to finish the second 10 problems (the back side) of the  Moles Conversions Worksheet (found on semester 1 Docs). You can also watch the Voicethread on mole conversions using the App or the semester 1 Notes Page.

After the excitement of MOLE DAY, it’s time to actually start using those friendly moles to our benefit. Today, we’ll be finishing the third part of our Mole lab with Cu/Fe. As a part of that lab, we’ll need to calculate how many moles of Cu/Fe were produced using the amount of grams of each.

To calculate grams to moles we use the FACTOR LABEL method. Let me show you what I mean…

Lets say you weighed your sample and have 105.5 g Cu atoms (Its important to label your values this way for future use; we’ll always add the element and “atoms” after the unit) and we want to know how many moles that is. well what do we know…

105.5 g Cu atoms   ->   ??? mol g Cu atoms

Well… lets think about this. Do we know how many grams are in 1 mol Cu atoms so we have something to compare this to??? Let’s look at our handy-dandy periodic table; find Cu; the atomic mass listed there is equal to the weight of 1 mol Cu atoms!

1 mol Cu atoms
63.5 g Cu atoms

So lets put this value into our formula and see if we can make this work…

105.5 g Cu atoms   x  1 mol Cu atoms
1                                  63.5 g Cu atoms

We can cross out the “g Cu Atoms” units so the only unit remaining is “mol Cu atoms“. So…

105.5 x 1 mol Cu atoms       = 1.66 mol Cu atoms
63.5

___________Easy! When you go from grams to moles you DIVIDE BY THE ATOMIC MASS!_______________
But, what if I want to go from moles to grams??? EASY!!! MULTIPLY BY THE ATOMIC MASS!
What is the weight of 2.5 moles of Carbon atoms?

2.5 mol C atoms x 12.0 g C atoms  =  30.o g C atoms
1                           1 mol C atoms

Since, 1 mole of any element = atomic weight of that element, you can flip the equation to work for you! Since we have moles on the top left of the formula, we want moles on the bottom right so they can cancel out!

Your homework for tonight is to finish the first 10 problems (the front side) of the Grams to Moles Conversions Worksheet (found on semester 1 Docs).

You guessed it! Your TEST IS THIS FRIDAY! Today you will be given a study guide to help you start organizing your thoughts and to start preparing yourself for the test. This test is usually a fairly easy test, but there is a lot of information… so start preparing now!

Before we’re ready to take the test we still have 2 topics to cover; 1 we’ve already sorta covered, and 1 brand new. Today we’ll be covering the one you already know a little something about, Substances & Mixtures. You’ll be using your book to answer some questions and do some inferring about what a substance and/or mixture is and how they are different. The handout and overview are located on the documents page (a filled in version will be available on the notes page tomorrow).

On top of that, today you’ll be given a study guide (available on the docs page) and a copy of tomorrow’s lab for you  to review.