1. Chemistry 102 Dr. Don DeCoste 367J Noyes Lab decoste@illinois.edu 3-4 pm Tuesdays and Thursdays By appointment; open door policy http://chem.illinois.edu 1

2. To Do Continue reading Chapter 3. Text homework for Chapter 3. Quiz on Friday (1-3.4) Lon-Capa assignments #1, #2. 2

3. REACT James Scholar Honors credit. Volunteer project. Meetings: Feb 1, 2, or 3 at 7 pm in 217 Noyes Lab. 3

4. A Question For You… You have a 10.0 g sample of copper (Cu). Determine the mass of magnesium (Mg) such that the number of copper atoms equals the number of magnesium atoms. 4

5. Consider This… Does a methane molecule (CH 4 ) contain more hydrogen or more carbon? 5

6. Calculate… Determine the percent mass of oxygen in each of the following substances: H 2 O (water) H 2 O 2 (hydrogen peroxide) 6

7. Determining a Formula You have some “nitrogen oxide” and you want to figure out what it is (both the formula and the name). You know it is 30.4% nitrogen by mass. Provide the name of this compound. If you cannot, explain why not. 7

8. Percent Mass Nitrogen in N 2 O 4 Note: we need the molar mass to determine the molecular formula. 8

9. A Question For You… Octane (a constituent of gasoline) is a hydrocarbon (consists only of carbon and hydrogen). It has a molar mass of about 114 g/mol and is 84.12% carbon by mass. Determine the molecular formula for octane. 9

10. Clicker Question Substance AB 2 is 42.86% A by mass. Determine the percent B by mass for substance A 2 B. a) 14.28% B b) 25.00% B c) 28.57% B d) 57.14% B e) I do not know/I can’t get any of the above answers. 10