Sept 18: Solutions

Today we started with notes on the smart board (here’s a pdf copy).  We went over dissociation of ionic compounds and you did a piece of this activity.

Homework is to do page 1 in giant worksheet packet (although doing page 4 would also be good since we did enough in class for you to do that page as well).

If you need help with Dilutions – use your book (end of chapter 4) or watch video below:

If you need help with molarity:

Sept 12: What’s on the test, lab, practice quiz, etc.

Today we started with a practice naming quiz. When I went over the answers I also reviewed some naming rules and patterns

Next we prepared for lab – set up lab notebook, did pre-lab problems, etc.  We only had about 40 minutes to do the lab and there was so much difficulty in getting equipment found, set-up, etc. that only one group actually managed to get a melting point!  So we’ll try again tomorrow!

In the mean time, here are some more details on what is on your test on Monday

  • no safety questions,
  • No uncertainties
  • Sig figs and dimesional analysis only as they apply to mole calculation problems
  • No lewis structures
  • No organic functional group identification
  • Ions will be limited to the ones you can predict from the periodic table, transition metals and the BOLDED ones on this ion sheet.

I like all the topics we are studying to fit together in a nice neat package…here is the story for this unit.  You could use this as a study guide, even.

  1. How do we know that there are atoms? What evidence did Dalton have?
    1. Law of Definite Proportions
    2. Law of conservation of mass
  2. Part of Dalton’s hypothesis was that atoms combine in whole number ratios.  We can experimentally determine the percent by mass, but in order to determine whole number ratios we need….good atomic weights and the mole concept
  3. In order to get good atomic weights we needed to take into consideration the different “flavors” that atoms come in.  Various isotopes have different masses so we utilize a weighted average since we don’t just deal with one atom a time (usually).To get average atomic weights we use mass spectrometry (Dalton didn’t have this –  I don’t know how they did it!)
    1. Outline how Mass Spectrometry works –
    2. Determine relative abundance of various isotopes and calculate average atomic weight based on spectra
  4. The mole concept was developed because we generally are unable to measure just one atom at a time.  The mole was defined such that the mass on the periodic table, not only represented one atom, but also represented the mass in grams of a large collection of atoms.  It just so happens that the number of atoms in this collection is …
  5. Now that we have a way of counting atoms by weighing we can determine the whole number ratios in which they combine
    1. Empirical Formula  Problem
    2. Hydrates
  6. It turns out that some elements combine in the same proportion, but have different properties: glucose and fructose.  Thus, it is necessary to know not just ratios, but the actual number of atoms in the molecule.  For this we need the mass spectrometer again.
    1. The molecular ion peak on the spectra gives …
    2. Molecular formula problem
  7. Now we have a way of keeping track of the atoms in each molecule we needed to develop a systematic way of naming them.
    1. Nomenclature
  8. Knowing the molecular formula also allows us to understand many of the other chemical and physical properties these molecules have.  Many of these properties result from the ratio of one element to another.
    1. Mole ratio problems (How many atoms in 10.o grams of copper (II) carbonate?)

Sept 11: Work on Empricial formula virtual lab

Today we spent the short class completing the empirical formula virtual lab you started last class.

I also handed out the lab for next class (Analysis of Alum) and a worksheet to help you with vocab on hydrates.

Homework: Finish virtual empirical formula lab, read alum lab, you may also need to read the page in the textbook on hydrates.  If you have extra time – memorize those ions!!

Sept 10: Empirical Formulas

Agenda:

  1. Hand out unit outline and objectives (google doc of objectives)
  2. Finish with Mass Spectrometry – how to get molecular weight (molecular ion)
  3. Law of definite proportions, relationship with atomic theory
  4. Quick notes on determining empirical or molecular formula (check website, unit 2 for videos)
  5. Lab notebook information and set-up, rubricLab Checklist
  6. Empirical formula Simulation Lab
    1. Virtual Lab
      1. Read the experiment description (scroll down a bit past the theory)
      2. Make a data notebook entry for this.
      3. For procedures: give reference URL and summarize the process
        1. What happens? What is measured?
        2. How is the mass of CO2 used to determine the moles of carbon in the original sample?
        3. How is the mass of water used to determine the moles of H in the original sample?
        4. If you know the mass of the carbon and the mass of the H in the original sample, how do you find the mass and moles of Oxygen?
      4. Data Collection: Do one random compound that has 3 elements.  (the random option will allow you to see the formulas to check your work)
        1. No qualitative observations, uncertainty or error prop required
      5. Data Processing Show calculations for empirical and molecular formula

Homework: Work on end of chapter problems (See unit outline. These will be due Monday before your test).  Also read sections 2.6 and 2.7 for a refresher on the difference between ionic and covalent bonding (molecules vs. formula units) or watch18 minutes of this video: (a live lecture)

Sept 7: Mass spec and unit analyisis practice

Agenda:

  • Warm-up: Hard mole problems
      1. If you have 50.0 g of Copper and 300. g of Nickel, how many total atoms do you have?

      (ans: 3.55 x1024 atoms)

      1. If you have 300. mg of Cobalt and 4.756 x 1021 atoms of Zinc, how many moles of atoms do you have?

      (ans: 1.299 x 10-2 moles)

      1. If you have 4.2 x 1016 molecules of compound b, how many nanomoles do you have (109 nanomoles = 1 mole)?

      (ans: 70. nmol)

    • 4.It was found that 7.0 x 1024 atoms of an unknown element had a mass of 46.5 g.  Identify the element and explain how you know. (He)
  • Derivation of 6.02 x1023
  • Mass Spectrometry– how we figure out isotopic abundances  (Answers to exercise 2: 6.82 amu)
    • A detailed lecture on mass spectrometry (first 20 min on how they work, next 10 minutes on interpreting atomic mass spec, YOUTUBE)
    • Another, much simpler lecture below on Mass Spec and Isotopes, but doesn’t show how to interpret spectra


Homework: Review naming (section 2.8 and worksheet), average atomic mass, finish density lab

A live lecture on naming with transition metals:

Sept 6th

Stuff to know:
  • •Unit objectives are available thru website or blog, (google doc, will continue to update)
  • •Need to memorize ions
  • Will have access to equation sheet and PT on part of your tests
  • Tonight’s homework: Finish Density lab, review average atomic mass and moles (watch videos) we’ll do practice next class

Today’s agenda

  • Review matter concepts (matter web)
  • Finish Data Collection for Density lab

Homework: Finish density lab error analysis, review moles, average atomic mass – see videos below (keep in mind these videos were done for my chem 1 class at GMHS so some of the things I say like, “you’ll learn in IB chem…” are not accurate!

averageAtomicMass from Maggie Wiseman on Vimeo.

Moles Honors from Maggie Wiseman on Vimeo.

Sept 5th

Today we started with a little warm-up problem – a pretty challenging dimensional analysis problem.  Some of you need to review so here are some resources:

Read the textbook – section 1.8 and do the corresponding problems – answers are in the back of the book for the blue numbered problems.  

Here’s a video lecture: start at minute 2:50 or so…

dimensionalAnalysis from Maggie Wiseman on Vimeo.

Next we went over the safety presentation and took the safety quiz.

After a brief review of measurement (uncertainties and sig figs) you spent the rest of class working on the density lab.   Technique video I showed is available here.

Homework: Finish pre-lab.  Work on recalling dimensional analysis and sig fig rules (see above)