Chemistry 202 Dr. Don DeCoste 3014 Chemistry Annex decoste@illinois.edu 11am-12pm Mondays and Wednesdays (after lecture) 10-11 am Tuesdays and 1-2 pm Thursdays By appointment; open door policy

Lon-Capa 1st HW assignment due Friday, 9/8, 10 pm. It is open now. 1st “Quiz” (2nd HW) due Sunday, 9/10 by 10 pm. It will open Friday, 9/8 at 5 pm.

For Today Textbook Homework Videos Introductory Material Chapter 2: 16, 17, 59, 60, 70 Chapter 3: 37, 44, 47, 59, 61, 94, 112, 135   Videos Introductory Material Chapter 3: Stoichiometry Stoichiometry I: Mass to Mass Conversions Stoichiometry II: Limiting Reactants

For Friday Textbook Homework Videos Chapter 3: Stoichiometry   Videos Chapter 3: Stoichiometry Problem Solving in Stoichiometry I: The Set-Up Problem Solving in Stoichiometry II: Method 1 Problem Solving in Stoichiometry III: Method 2 Problem Solving in Stoichiometry IV: Method 3

Three Big Topics Stoichiometry: information on “what” happens; allows us to determine amounts of reactants and products. Thermodynamics: information on “why” reactions happen; allows us to make predictions about whether a reaction will occur. Kinetics: information on “how” reactions happen (mechanisms); relates to the speed of reactions.

Three Big Themes Content: specific topics in chemistry. Models: a way of explaining the phenomena we observe; theories. Understand significance and limitations. Problem Solving: be able to solve novel problems in a creative and flexible way using conceptual understanding of fundamental ideas; Challenge Problems in the text are good for this.

Problem Solving: A Journey Where Are We Going?: What are we trying to solve? What does this mean? Where Have We Been?: What do we know? What is given in the problem, and what is our knowledge base? How Do We Get There?: How do we connect what we know to what we are trying to solve? Diagrams and more questions can be useful.

“Well, lemme think. … You’ve stumped me son “Well, lemme think. … You’ve stumped me son. Most folks only wanna know how to go the other way.”

Clicker Question A metal ion has 23 electrons in an ionic compound that is 30.06% oxygen by mass. Which metal is in the compound? a) Vanadium b) Chromium c) Manganese d) Iron e) Cobalt  

Make Sure You Understand This… Determine the percent mass of oxygen in each of the following substances H2O (water) (88.81%) H2O2 (hydrogen peroxide) (94.07%)