The!Mad!Scientist!
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The!Mad!Lab!

IB Chemistry G12

September 13-15, 2015

9/13/2015

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Housekeeping: We need to discuss what's happening after Eid.  Also, we can't get into the lab today to analyze our experimental findings, so hopefully we can do it tomorrow.

Lesson Review:  Socrative    Teacher Code: LR2E0KJH

Agenda:
1.  Review the previous lesson.
2.  Discussion of empirical & molecular formulas.

Lesson Objectives:
1.  Distinguish between empirical formulas and molecular formulas.
2.  Determine the empirical formula of a compound.
3.  Explain what percent composition means in terms of a compound.
4.  Determine the molecular formula of a compound.

Content Review:
Links:  Empirical & Molecular Formulas    Percent Composition
Textbook Readings: 1.2; p. 20-27

Student Missions:
Mission 1:  Formulas, formulas, formulas.  When we look at chemical formulas, we should be looking at the empirical formula.  This is the simplest whole number ratio of elements in a compound.  The molecular formula gives the actual number of atoms in a molecule.
Let's practice!  Look at pages 22-23 in the text.

Mission 2: Well, how much is it though?  Percentage by mass data is the most common way to deduce the ratio of atoms present in a compound.  But what about when you're given a percentage of an element in a compound?  How do you determine the accuracy of such a statement?

Well, you use percent composition.  The percent by mass of an element in a compound depends on the total contribution of that element's atoms.  Here is a short example on percent composition basics.
Working at the IB level, may I present Mr. Richard Thornley.
Mission 3: It's MOLECULAR!  Molecular formulas, as stated in Mission 1, show all of the atoms present in a molecule.  It has a simple formula (p. 25 in your text) that multiplies an integer by the mass of the empirical formula.  Sound complicated? Sure it does, but it actually isn't.  Take a look...Mr. Thornley's in the Mad!Lab! again.
Let's practice.  Chem Team has some problems with solutions provided, including steps.
Bergen.edu also has some practice problems with solutions provided.  I expect for you to work through these problems and show me your work next class.  If there are questions, ask them.

9/13 Homework:  Complete the practice problems.  Work them out step by step.  There will be a Socrative review on today's material.  Hopefully we can get back in the lab to analyze our results.
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