1. Announcements Post/Pre-lecture assignment due Tuesday
Workshop in Lab on Monday
Exam 1 grades posted
Look at scaled score out of 100 points
Get exams back in discussion tomorrow
Liquid nitrogen ice cream winner is…
What is the purpose of the quicksand video?

2. “Read” the following reactions in words.
2P(s) + 5O2(g)  P2O5(s)
2NaNO3(s)  2NaNO2(s) + O2(g)
2Al2O3(s) + 3C(s)  4Al(s) + 3CO2(g)

3. 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.

4. Example #2
Write and balance: solid magnesium reacts with nitrogen gas to form solid magnesium nitride.

5. Clicker #1
Which of the following shows the correctly balanced equation for this reaction:
H2O2 → H2O + O2
A) 3 H2O2 → 3 H2O + O2
B) H2O2 → 2 H2O + O2
C) 2 H2O2 → 2 H2O + O2
D) H2O2 → H2O + O2

6. Clicker #2
Solid magnesium reacts with oxygen gas to form solid magnesium oxide. Write and balance this equation, including phases. What is the sum of the coefficients when balanced in standard form? 3 4 5 6 7

7. Clicker #3
What is the correct unbalanced chemical equation for the reaction of iron(II) oxide with oxygen gas to produce iron(III) oxide?
A) FeO + O2 → Fe2O3
B) FeO2 + O2 → Fe2O3
C) FeO2 + O2 → Fe3O2
D) FeO + O2 → Fe3O2
E) FeO2 + O2 → FeO

8. Clicker #4
Balance the following equation and determine the sum of the coefficients:
C2H5OH + O2 → CO2 + H2O
A) 4
B) 5
C) 8
D) 9
E) 10
This is a quick way for us to see if you balanced the equation correctly.

9. Clicker #5
Which of the following shows the correctly balanced equation for this reaction:
CaC2 + H2O → C2H2 + Ca(OH)2
A) CaC2 + H2O → C2H2 + Ca(OH)2
B) CaC2 + 2 H2O → C2H2 + Ca(OH)2
C) 2 CaC2 + H2O → C2H2 + 2 Ca(OH)2
D) 3 CaC2 + 3 H2O → C2H2 + 3 Ca(OH)2

10. Discussion #1
Which of the following diagrams best represents the chemical equation N2 + H2 → NH3 after it is balanced?
1) →
2) →
3) →
4) →
5) →