Course Icon


Chapter 2: 6-10

SO Icon


Molecules, Moles, and Composition Analysis

Chapter 2: Section 10 Homework

Reading Preparation

Textbook assignment: Read Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 2: Section 10.

Study Notes

Important Formulae

Concept Formulae or Notation Explanation
Mass to Moles Conversion moles     grams mole   =   grams

grams     moles grams   =   moles

grams/mole is the molar mass, equal to the atomic weight in grams listed on the periodic table
Percent Composition #   moles   element   mole   of   molecule     molar   mass   of   element mole   of   element   =   grams   of   element mole   of   molecule molar mass = grams/mole of element
Mass percent of element in compound mass   percent   =   grams   of   element    molar   mass   of   compound The percent masses for all elements in the compound should add up to 100%.

Web Lecture

Read the following weblecture before chat: Atoms, Molecules, and the Mole

Study Activity

Videos for Chapter 2

Use the simulation below to build molecules.

  • Click on the "Single" option.
    • Build the water molecule by moving the atoms up into the central design area. Click on the 3D option to see your molecule in 3D. Drag it in the 3D display to examine its shape. Click on the "bond" option to show the bonds between atoms. How many bonds are there between each H and the O atom? Close the 3D display and drag the water molecule to its position in the "collection".
    • Click on the right arrow in the tray area to get a new set of atoms. Build the oxygen and hydrogen gas molecules. Examine the bonds and shape of your molecules in 3D.
    • Click on the right arrow in the tray area to get a new set of atoms. Build the carbon dioxide and nitrogen gas molecules. Examine the bonds and shape of your molecules in 3D.
    • Build at least one more collection.
  • Click on the "Multiple" option.
    • Build the required molecules for your collection. Refill the supply pans if necessary with the yellow arrow, lower left.
  • With the "Playground" option, see how many different molecules you can build with the atoms supplied. When you have a legitimate molecule, the display will name it and allow you to view it in 3D. What are the names of the atoms you've created? Which ones have double bonds? Do any have triple bonds?

General notes:

Be sure that you work through all the examples and understand them, and read the problem-solving tips! The more foundation work you lay now, the less trouble you will have later on.

If you've never seen Coulomb's Law before (p. 78), don't be confused by the format here; it is really a simple relationship that says the force between two charges is equal to the product of the charges (q1*q2) divided by the square of the distance between them, and multiplied by a constant that depends on the units we use to measure the charge and distance: Fe= kQq/r2. It's similar to the inverse square law that governs gravity and for the same reason: we have a point source for the force.

Chat Preparation Activities

Chapter Quiz

Lab Work

Develop your skills with distillation and recrystallization techniques. Working with your teacher and teammates, design a lab to extract a target component from a solution or mixture.

References: Illustrated Guide to Home Chemistry Experiments [Required text], or Home School Chemistry Kit Manual which comes with the Home Scientist Chemistry Kit CK101 set and is available online at The Home Scientist.

You may find some of the basic lab skills described in Lab Techniques 1: weighing samples, filtering solutions, and cleaning equipment and Lab Techniques 2: Reading thermometers, handling hot equipment, using the Q test useful as well.