The document provides an overview of a chemistry lesson on balancing chemical equations, including examples of balancing the equations H2 + O2 → H2O and H2 + Cl2 → HCl. It outlines the 3-step process for balancing equations: counting atoms on both sides, changing coefficients and multiplying, and checking the tally. Practice questions are assigned as homework.

1. Launch: 11/17
 Grab your binder and immediately take a seat!
 Place homework (practice questions) on desk.
Mg + 2H2O  Mg(OH)2 + 2H2
3. Is the above equation balanced?
a. No, because the number of H atoms is not equal
b. No, because the number of O atoms is not equal
c. Yes, because the number of Mg atoms is not equal
d. Yes, because there are equal numbers of atoms on
both sides of the equation

2. Launch 11/17
4. Hydrogen gas (H2) and oxygen gas (O2) react to
form water (H2O). Which of these represents a
properly balanced equation for this reaction?
a. H2 + O2  H2O
b. 2H2 + 2O2  2H2O
c. 2H2 + O2  2H2O
d. H2 + 2O2  2H2O

3. Announcements
 Unit #5: Chemical Reactions & Stoichiometry
 Class points end next week
 Get your HW done
 Be respectful
 Quiz on Friday!

4. How are equations
balanced?
Mr. Heffner
11/17/09

5. Review
 Is the below equation balanced?
Cl2 + H2  2HCl
2 X Cl 2XH 2XH
2 X Cl
Multiply the
coefficients and
subscripts
Yes, it is balanced!

6. 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)
Only one rule: you can’t change the subscripts

7. Example #1
 Balance the equation,
H2 + O2  H2O

8. Example #1
 Step #1: Count the atoms on both sides
H2 + O2  H2O
2XH 2XO 2XH
1XO
Unbalanced!it underneath
Put

9. Example #1
 Step #2: Change coefficient & multiply out
H2 + O2  H2O
2
2XH 2XO
(
2XH
2X 1 X O )
4XH
2XO

10. Example #1
 Step #3: Check tally (and repeat)
2H2 + O2  H2O
2
(
2X 2 X H ) 2XO 4XH
2XO
4XH
Still unbalanced!

11. Example #1
 Step #3: Check tally (and repeat)
2H2 + O2  H2O
2
4XH 2XO 4XH
2XO
Balanced!

12. Activity
 Make the equation on your whiteboard
 Balance the equation with the 3-step method
1. Count the atoms
2. Add a coefficient
3. Check tally (and repeat)
 Raise hand to get checked off
 Record reactants, products, and final balanced
equation on worksheet

13. Practice Questions
 Practice question handouts

14. Exit Slip
1. In a balanced equation
a. the reactant atoms are destroyed to make the
products
b. the number of atoms on the reactants side of the
equation is equal to the number of atoms on the
products
c. the number of atoms on the reactants side of the
equation is not equal to the number of atoms on the
products
d. all compounds have a coefficient of at least 2

15. Exit Slip
H2 + Cl2  HCl
2. 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.
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.

16. Exit Slip
4K + O2  2K2O
3. In the already balanced reaction above, what is the
coefficient for O2?
a. 0
b. 1
c. 2
d. 4

17. Exit Slip
__C + __Br2  __CBr4
4. When the equation above is completely balanced,
the coefficient for Br2 would be
a. 0
b. 1
c. 2
d. 4

18. Exit Slip
__Na + __H2O  __NaOH + __H2
5. When the above equation is completely balanced,
the coefficient for NaOH would be
a. 1.
b. 2.
c. 4.
d. 8.

19. Homework
 Finish practice question worksheet