The document contains information from a chemistry class, including: - A practice exam average of 87% was achieved, with questions 5, 6, 7, 9, and 14 dropped. - An upcoming unit exam on Thursday will cover balancing equations, the mole concept, and conversions between grams, moles, atoms, and grams. - A snowman challenge activity had students work in groups to balance sample chemical equations. - An exit slip posed sample questions testing the concepts of identifying reactants, calculating atoms in a formula, balancing equations, and determining missing coefficients.

1. Launch: 12/14
 Grab your binder and immediately take a seat!
 Place binder paper and a pen/pencil on your desk.
Review Objective #1: I can write balanced chemical
equations.
Tonight’s HW: Finish Review Worksheet #1

2. Launch 12/14

3. Launch 12/14
16. How many grams does 2 moles of soda niter
NaNO3 weigh?
a. 17g
b. 85g
c. 170g
d. 1700g

4. Launch Answers

5. Launch Answers
16. How many grams does 2 moles of soda niter
NaNO3 weigh?
a. 17g
b. 85g
c. 170g
d. 1700g

6. Practice Exam Results: B1
 Our goal = 80%
 Our average = 86%
 Questions dropped
 5, 6, 7, 9, 14

7. Practice Exam Results: B1
 Our goal = 80%
 Our average = 78%
 Questions dropped
 5, 6, 7, 9, 14

8. Practice Exam Results: B1
 Our goal = 80%
 Our average = 87%
 Questions dropped
 5, 6, 7, 9, 14

9. Practice Exam Results: B1
 Our goal = 80%
 Our average = 88%
 Questions dropped
 5, 6, 7, 9, 14

10. Announcements
 Unit #5 Exam on Thursday
 3 days to review
 Ask questions!
 No copying HW or classwork!
 Make-up work is due on Wednesday
 Binder check this week

11. Exam Information
 30 multiple-choice questions
 Balancing equations (6 questions = 20%)
 The mole (9 questions = 30%)
 Conversions (15 questions = 50%)
 gram  mole (6 questions)
 gram  atoms (3 questions)
 gram  gram (6 questions)
 3 free response

12. Review:
Balancing Equations
Mr. Heffner
12/14/09

14. What’s a chemical equation?
CH4 + 2O2  CO2 + 2H2O
Reactants Products
“turn into”

15. What’s a chemical equation?
4Fe2(CO3)3
Coefficient
 Multiply! Subscript
 8 X Fe
 12 X C
 36 X O

16. How are equations balanced?
 There is a 3-step process for balancing
equations:
1. Count the atoms on both sides
2. Change a coefficient & multiply out
3. Check tally (and repeat)
Rule: You can’t change the subscripts!

17. Example
 Balance the equation,
N2 + H2  NH3

18. Example
 Step #1: Count the atoms on both sides
N2 + H2  NH3
2XN 2XH 1XN
3XH
Unbalanced!

19. Example
 Step #2: Change coefficient & multiply out
N2 + H2  NH3
2
2XN 2XH
(
1XN
2X 3 X H )
2XN
6XH

20. Example
 Step #3: Check tally (and repeat)
N2 + H2  NH3
3 2
( )
2 X N 3X 2 X H 2XN
6XH
6XH
Still unbalanced!

21. Example
 Step #3: Check tally (and repeat)
N2 +3H2  NH3
2
2XN 6XH 2XN
6XH
Balanced!

22. Snowman Challenge
 Directions:
 Send one group member to pick a card
 Write down the equation and #
 Balance it showing all work (count, coefficient, check)
 When finished, send one group member to have me
check your answer
 Rules:
 If you pick it, solve it
 Only one card at a time
 Show your work!
 Work together

23. Exit Slip
HC2H3O2 + NaHCO3  NaC2H3O2 + H2CO3
1. Which of the following correctly identifies all of
the reactants in the above chemical equation.
a. NaC2H3O2
b. NaHCO3
c. NaC2H3O2 and HC2H3O2
d. HC2H3O2 and NaHCO3

24. Exit Slip
2. How many C atoms are there in 3C2H4?
a. 2
b. 3
c. 5
d. 6

25. Exit Slip
H2 + Cl2  HCl
3. Is the above equation balanced?
a. No, because H2 has a coefficient of 2.
b. No, because the number of Cl and H atoms are not
equal on both sides of the equation.
c. Yes, because the number of H atoms is not equal on
both sides.
d. Yes, because there are equal numbers of atoms on
both sides of the equation.

26. Exit Slip
4. Which of the following is a balanced equation for
the combustion of ethanol (C2H6O)?
a. C2H5OH + 3O2  CO2 + 2H2O
b. C2H5OH + 3O2  2CO2 + 3H2O
c. C2H5OH + O2  2CO2 + 3H2O
d. C2H5OH + 2O2  3CO2 + 2H2O

27. Exit Slip
__C2H2 + __H2  __CH4
5. When the equation above is completely balanced,
the coefficient for H2 would be
a. 1
b. 2
c. 3
d. 4

28. Homework
 Finish practice questions worksheet