INTRODUCTION: Chemistry is a quantitative science. We measure specific amounts of grams of chemicals to react with other chemicals. We measure temperature, volume, pressure and changes in mass. All these measurements require numbers and units. Some of these quantities are unique to Chemistry and others are found to other disciplines. One quantity, which is especially important and unique in Chemistry, is the “mole”. The mole is a means of counting. Atoms are far too small to individually count, so we count atoms, molecules and compounds in larger groups. Just like we count larger amounts of eggs in dozens or gross, we count chemical particles in “moles” in order to allow us to work with measurable quantities of chemicals. When chemicals react they react in a whole number ratio, which is related to the number of moles. However, we measure reactants and products in a chemical reaction in terms of mass in grams. Stoichiometry is the calculation of quantities in chemical equations that interchanges units between mass and moles. Whenever chemists produce chemicals whether for chemical industry or in the pharmaceutical industry, they make sure that they have the appropriate amounts of reactants in order to produce the desired amount of products at the minimum cost. Stoichiometry is the essential mathematical tool of the chemist to determine these quantities.
OBJECTIVES:
As you study this unit, you should be able to do the following:
Define a “mole” and relate it to Avogadro’s number. (10-1)
Define molar mass and tell how it relates to the mass of a substance. (10-1)
Convert among an number of particles, moles and mass of a substance. (10-2)
Convert moles to volume and volume to moles, using the volume of one mole of a gas at STP (22.4 L). (10-2)
Calculate the percent composition of a substance from its chemical formula or experimental data. (10-3)
Derive the empirical and/or molecular formula of a compound from experimental data. (10-3)
Interpret balanced chemical equations in terms of interacting moles, representative particles, masses and volume (gases at STP). (11-1)
Calculate stoichiometric quantities from balanced chemical equations using units of moles, mass, representative particles and volume (gases at STP). (11-2)
Draw atomic level pictures that represent chemical reactions in terms of proportions of reactants and products including states, types and formulas of compounds.
Use atomic level pictures to identify the limiting reagent in a reaction and to quantify the amount of excess reagent(s). (11-3)
LEARNING ACTIVITIES:
To learn about objectives 1-6:
READ Chapter 10, pp. 311-339. See objectives for specific section.
WRITE "Problem Solving Using Conversions and Dimensional Analysis" Worksheet.
READ and PERFORM lab “Molar Quantities: Weighing as a Means of Counting”.
READ and PERFORM Lab, “Determining the Formula of a Hydrate.”
WRITE GIA 5-2.5: "Determining Empirical and Molecular Formulas"
WRITE answers to end of the chapter question #s 17-22, 30,33, 35, 38-40, 42,43, 45-49, 51 found on pp. 343-345.
To learn about objectives 7-10:
READ Chapter 11, pp. 347-373.
WRITE GIA 5-3: Stoichiometry and Answers
WRITE GIA 5-4: Limiting Reactant and Answers
WRITE GIA 5-6: Visualizing Quantities in Chemical Reactions and Answers
READ and PERFORM lab “Making a Pet Balloon”
WRITE answers to end of the chapter question #s 15-16, 30, 31, 34, 36, 38-40, 44, 46, 48, found on p. 377-379.
To make sure you understand the objectives for this unit:
ASK me, the teacher, any lingering QUESTIONS
TAKE the Unit’s Self-Test
