Chemistry 202 Dr. Don DeCoste 367J Noyes Lab decoste@illinois.edu 11am-12pm Mondays and Wednesdays (after lecture) 10-11 am Tuesdays and 1-2 pm Thursdays By appointment; open door policy

Join the ACS Student Chapter! First grand activity of the year BBQ on the quad – August 25th 5 pm outside of Noyes Lab Come to our BBQ and Chapter Meeting to find out all that we do!

Lon-Capa 1st HW assignment due Friday, 9/2, 5 pm. It is open now. 1st Quiz due Sunday, 9/4 by 10 pm. It will open Wednesday, 8/31 at 5 pm.

For Friday Continue working on Lon-Capa. Continue reading Chapter 3 and doing the Chapter 3 homework. Chapter 3: 63, 65, 74, 75, 81, 82, 87, 100, 125, 126, 140 See me or email me if there are any questions or concerns. Video on Limiting Reactants

Using The Periodic Table

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.

Big Ideas of Mole Concept We can count by weighing (relative masses). Reactions occur by number of particles, we often deal with masses. [We will deal with solutions (Chapter 4) and gases (Chapter 5) as well]

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%)

Make Sure You Understand This… The hydrogen peroxide we use in lecture is a 30% by mass aqueous solution of H2O2. If we decompose 50.0 g of 30% hydrogen peroxide solution, determine the mass of oxygen that is produced. (7.06 g)

Clicker Question Which of the following is closest to the mass of electrons in an adult human? A) About a milligram (0.001 g) B) About a gram C) About an ounce (~20 to 30 g) D) About a pound (~400 to 500 g) E) About 10 pounds (~4 to 5 kg)

A Question for You… Estimate the mass of electrons in an adult human and provide support for your estimation.