1. Announcements Lon Capa HW #4 has been opened. Lab this week! Follow dress code.

2. What Does a Chemical Equation Tell Us? Formulas for reactants (left side) Formulas for products (right side) Relative amounts of reactants and products Phase (sometimes)

3. What Does it Mean to be “Balanced”? Same number of each type of atom on each side (Law of Conservation of Matter)

4. How Do We Balance Chemical Equations? Mainly trial and error (some general strategies though) Make sure you have same number of each type of atom on both sides of equation Do not balance by changing the subscripts! Balance the least complicated molecule LAST.

5. Clicker #1 Which of the following shows the correctly balanced equation for this reaction: H 2 O 2 → H 2 O + O 2 A) 3 H 2 O 2 → 3 H 2 O + O 2 B) H 2 O 2 → 2 H 2 O + O 2 C) 2 H 2 O 2 → 2 H 2 O + O 2 D) H 2 O 2 → H 2 O + O 2

6. Clicker #2 Balance the following equation and determine the sum of the coefficients: C 2 H 5 OH + O 2 → CO 2 + H 2 O A)4 B)5 C)8 D)9 E)10

7. Why wear safety equipment? Supposed to be the combustion of ethanol… http://chem.illinois.edu/SABICstudio/101/ safety.html

8. Clicker #3 What are the possible products? AgNO 3(aq) + KCl (aq) → ? A) AgCl and KNO 3 B) AgNO 3 and KCl C) AgK and NO 3 Cl D) Any of the above could be the products.

9. Clicker #4 So what is true about KNO 3 ? A) KNO 3 is aqueous (soluble) in all three reactions. B) KNO 3 is the solid in reactions 1 and 2 but not reaction 3. C) KNO 3 is the solid in reaction 1 but not in reactions 2 and 3. D) KNO 3 is the solid in reaction 2 but not in reactions 1 and 3 E) KNO 3 is the solid in reaction 3 but not in reactions 1 and 2.

10. Solubility Rules (Page 172) 1. Most nitrate salts are soluble. 2. Most salts of sodium, potassium, and ammonium cations are soluble. 3. Most chloride salts are soluble. Exceptions: Ag + and Pb 2+. 4. Most sulfate salts are soluble. Exceptions: Ca 2+, Ba 2+, and Pb 2+. 5. Most hydroxide salts are only slightly soluble. Soluble ones are: Na +, K +, and Ca 2+. 6. Most sulfide, carbonate, and phosphate salts are only slightly soluble.

11. Precipitation Reactions  Know how to use the solubility rules (you will be given them on the exam).  Know how to write equations from reactants (ionic reactants).  Understand what solutions “look” like at a very magnified level.