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

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.

Chemistry Learning Center 230 Davenport Hall Chemistry TAs available from 9 am – 5pm Mondays – Fridays. Link to the schedule is on the website (Contact Information) Chemistry 202 TAs in the CLC: Mondays: 1pm-3pm Wednesdays: 3pm-5pm Thursdays: 11am-1pm Fridays: 1pm-3pm

For Monday Continue working on Lon-Capa. Finish Chapter 3 and start Chapter 4 Chapter 3: 103, 104, 124, 129, 132, 137 Chapter 4: 3, 5, 17, 21, 26, 30, 91 Chapter 4: precipitation stoichiometry Bring any questions from Chapter 3 to lecture. See me or email me if there are any questions or concerns.

Clicker Question Which of the following is closest to the mass of electrons in an adult human? 56% A) About a milligram (0.001 g) 26% B) About a gram 10% C) About an ounce (~20 to 30 g) 6% D) About a pound (~400 to 500 g) 2% E) About 10 pounds (~4 to 5 kg)

Potentially Useful Information Mass of electron = 9.10939 x 10-31 kg Mass of proton = 1.67262 x 10-27 kg Mass of neutron = 1.67493 x 10-27 kg Ratio of mass e– to mass p+/n = 1:1836

Chemical Reaction

Clicker Question Balance the following equation in standard form and determine the sum of the coefficients: C2H5OH + O2 → CO2 + H2O A) 4 B) 5 C) 8 D) 9 E) 10

Make Sure You Can Do This… 500.0 g of hydrogen gas and 500.0 g of oxygen gas are reacted to form water. Determine the mass of water produced (563.0 g) and the mass of excess reactant left over (437.0g H2). Prove mass has been conserved. (500.0 g + 500.0 g = 563.0 g + 437.0 g)

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?

Office Hours: My Contribution Yes you can. What are you looking for? OK, write that down … So what does this mean? OK, write that down. OK … Sure, no problem at all.

Challenge Problem: Ch. 3 #130