12 14 Balancing Review
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Transcript of 12 14 Balancing Review
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
Launch 12/14
Launch 12/14 16. How many grams does 2 moles of soda niter
NaNO3 weigh? a. 17g b. 85g c. 170g
d. 1700g
Launch Answers
Launch Answers 16. How many grams does 2 moles of soda niter
NaNO3 weigh? a. 17g b. 85g c. 170g
d. 1700g
Practice Exam Results: B1 Our goal = 80%
Our average = 86%
Questions dropped 5, 6, 7, 9, 14
Practice Exam Results: B1 Our goal = 80%
Our average = 78%
Questions dropped 5, 6, 7, 9, 14
Practice Exam Results: B1 Our goal = 80%
Our average = 87%
Questions dropped 5, 6, 7, 9, 14
Practice Exam Results: B1 Our goal = 80%
Our average = 88%
Questions dropped 5, 6, 7, 9, 14
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
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
Review: Balancing Equations
Mr. Heffner 12/14/09
CH4 + 2O2 CO2 + 2H2O
What’s a chemical equation?
Reactants Products “turn into”
What’s a chemical equation?
4Fe2(CO3)3
Multiply! 8 X Fe
12 X C 36 X O
Coefficient Subscript
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!
Example Balance the equation,
N2 + H2 NH3
Step #1: Count the atoms on both sides
N2 + H2 NH3
Example
2 X N 2 X H 1 X N 3 X H
Unbalanced!
Step #2: Change coefficient & multiply out
N2 + H2 NH3
Example
2 X N 2 X H 1 X N 3 X H
2
2 X N 6 X H
2X( )
Step #3: Check tally (and repeat)
N2 + H2 NH3
Example
2 X N 2 X H
2
2 X N 6 X H
3
6 X H
Still unbalanced!
3X( )
Step #3: Check tally (and repeat)
N2 + H2 NH3
Example
6 X H
2
2 X N 6 X H
3
2 X N
Balanced!
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
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
Exit Slip 2. How many C atoms are there in 3C2H4?
a. 2 b. 3
c. 5 d. 6
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.
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
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
Homework Finish practice questions worksheet