1. What is the definition of molarity ? Concentration factors like molarity are defined in terms of two of the following: solute, solvent and solution. Specifically, molarity is defined as the number of moles of solute divided by the volume of the solution in liters. Molarity is given by the symbol, M or the unit cluster mols/liter. In Chemistry 211 to 213, the type of solution considered is a "binary" or two component solution consisting of a single, solute dissolved in a solvent. In many situations in general chemistry, the solvent is water and the resulting solution is called an aqueous solution with the solute concentration given as mols/liter or M, molarity.

2. What information do I need to find the molarity of some solution ? As you work through the exercises in this unit, you will realize you need to know the mass of the solute in grams and its molar mass as well as the final volume of the solution given in the volume unit of liters.

3. Why is the concept of a solution presented with "stoichiometry" ? Stoichiometry encompasses many quantitative calculations used in chemistry including the methods for converting moles of one substance to another using a balanced chemical equation . Molarity, with the units mols/ liter, provides another way to express the number of moles of some substance participating in a chemical reaction. If you know the concentration of a solution and how many liters of it are used, you know the number of moles of solute consumed . So "solution stoichiometry" is a simple extension of the stoichiometric concepts developed in Unit 3.

4. What is a titration ? A "titration" is the the quantitative measurement of the volume of a solution of known concentration which was added to a reaction mixture. The volume of solution delivered is generally measured in milliliters using a "buret" and the reaction is allowed to proceed to a "point" of completion as shown by an "indicator", a pH meter or some other kind of reaction monitor. (Note: A titration simulation is shown on Screen 5.15. When I "ran" the titration, the end-point occurred at 13.00 mls of base added not 12.50 mls, as suggested in the "summary". What do you find to be the end-point when you try the titration?)

5. Why are the FAQ's so short this time ? Most of the questions related to stoichiometry were addressed in Unit 3, "Frequently Asked Questions". Review them for this unit, also.

Return to Unit 4 Directory