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Series: Chemistry: Mass/Mole Relationship Problems

About this Series

  • Lessons: 6
  • Total Time: 0h 48m
  • Use: Watch Online & Download
  • Access Period: Unlimited
  • Created At: 10/22/2009
  • Last Updated At: 05/10/2011

This six part series will be all about solving problems involving mass/mole relationships. One of the first tools we'll need to learn is finding empirical and molecular formulas. Analysis by mass is used to determine the ratio of elements in a sample. The empirical formula is the chemical formula of a compound written with the simplest ratio of elements. The molecular formula is the exact atomic formula of a compound.

Building on the first lesson we will then move on to learning about stoichiometry and chemical equations. It is important to remember the following as we go through this lesson and as we further build on these concepts. Balanced chemical equations relate reactants and products in moles. Also, that molar ratios from balanced chemical equations can be used as conversion factors.

Next, we move on to finding limiting reagents. When two or more reagents are combined in a chemical reaction, one of them is the limiting reagent and will run out before the others (unless there are stoichiometric amounts of each). Determining how much product can be formed from the balanced chemical equation and the amounts of reagents available is the basis for the limiting- reagent problem in chemistry.

To help visualize and tie together what has been covered we have a demonstration or self inflating hydrogen balloons. The chemical reaction of magnesium and hydrochloric acid produces hydrogen gas, which can be collected in balloons. The sizes of the four balloons reflect the stoichiometry of this reaction. The balloons are an excellent way to see how limiting reagents and stoichiometry are actually used in a laboratory.

Now that we have a solid mental picture of what we're learning about we get to learn about theoretical yield and percent yield. Theoretical yield is the maximum amount of product that can be made from a given amount of reactants. Percent yield is the actual yield expressed as a percentage of the theoretical yield. Knowing and understanding this and the rest of these concepts will lead us into the final lesson.

Finishing off this series is a problem using the combined concepts of stoichiometry. You will use many of the tools and concepts covered in this series as well as from other lessons. This lesson is an excellent way to solidify what you've learned from this series and apply it to a real problem.

This series of lessons was selected from a broader, comprehensive course, Chemistry. This course and others are available from Thinkwell, Inc. The full course can be found at The full course covers atoms, molecules and ions, stoichiometry, reactions in aqueous solutions, gases, thermochemistry, Modern Atomic Theory, electron configurations, periodicity, chemical bonding, molecular geometry, bonding theory, oxidation-reduction reactions, condensed phases, solution properties, kinetics, acids and bases, organic reactions, thermodynamics, nuclear chemistry, metals, nonmetals, biochemistry, organic chemistry, and more. The course features three renowned chemistry professors: Dean Harman, a professor of Chemistry at the University of Virginia and Gordon Yee, an associate professor of Chemistry at Virginia Tech and Tarek Sammakia, a professor of chemistry at the University of Colorado at Boulder.

About this Author

2174 lessons

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Lessons Included

None of the lesson in this series have been reviewed.

Below are the descriptions for each of the lessons included in the series:

Supplementary Files: