Moles to Molecules

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.

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1 mole = 6.022 x 10-23 atoms = Atomic Mass

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…

2.56.022 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.

Moles to Grams… Grams to Moles

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).

Test Day!

Nice try.

In association with the shortened periods for Fall fest. I have adjusted the test so that it only has 45 questions worth 90 pts. total.

There will be calculations, but the test is entirely scantron (T/F, MC, & Matching).

Good Luck!

The Password is… “Positron”

Our review game for today is the old school game show “Password”.  The same Powerpoint used in class will be available after school via the semester 1 Documents page for you to review with. My suggestion would be:

  • If you’re by yourself, use the pages as flashcards and say what you know about each term out loud
  • If you’re with other chem students, give each other clues in the same way the game is played.

It’s important to point out that although the game is fun and a good tool to review vocab, most of your test will be based on performing problems and calculations. Make sure you can complete the following:

  1. When given an isotopic symbol, identify the number of Protons, Neutrons, & Electrons.
  2. Correctly change the number of electrons in Cations and Anions.
  3. Identify a common isotope using the atomic mass of an element, then rounding that number.
  4. Calculate atomic mass using actual atomic masses & percent abundance of isotopes
  5. Complete nuclear reactions (Alpha & Beta)
  6. Complete a nuclear decay scheme
  7. Identify particles by their symbol
  8. Complete a half-life chart.

Use your study guide and the answers from the documents page. Watch the voice threads and go over notes to help you review.
Please contact me via email if you have questions tonight. Feel free to come see me before school for extra help as well.

Test Friday! Start Studying!

Today we‘ll be finishing gathering our information on Nuclear Chemistry and begin working on our Unit 3 Study Guides. You’ll be receiving the study guide today (also available at the link below and on the Docs Page) in advance of your

UNIT 3 TEST FRIDAY!

 The Study Guide will be the second grade of the new 9 weeks, after we finish our Nuclear Decay activity on Tuesday. The test then will not only be the 3rd grade of the new quarter, but it will also be the first major grade of the new 9 weeks! The test will be 100pts. So, start prepping now. Review the Voicethreads, study the study guide, make not cards of the vocab, do whatever it takes… but start preparing now!

New-Clear!

Today we’ll be investigating the nucleus of the atom. I’m sure you know about the tradition powers…20121011-074923.jpg The proton, the neutron, & the electron. But, believe it or not, there’s more to the nucleus than meets the eye… Which is a weird statement since you can’t even see the nucleus, but I digress.
You’ll need

Skim the chapter and fill in the questions with information from the chapter. I am not asking you to read the entire chapter. Instead, Find the section you need, and skim the information. Then go to the questions, fill in the info you remember, and then go back to the text to get specific answers.

I Has Anser!

Yes, “I HAS ANSER!”
The answers to the particle caluclations are avaialble on the documents page. Also, the Atomic Mass answers are available there as well.

Reminder! Do not Just copy! Do the work on your own, and check your answers. It is more important to me that you get the info right and you understand how to do the steps, than to have you just do “busy work”.