The document provides information about chemical equations including: 1. A chemical equation represents a chemical reaction and shows the reactants on the left and products on the right of a reaction arrow. 2. Coefficients indicate the number of units of each element or compound and subscripts indicate the number of atoms in a molecule or compound. 3. Examples show how to use coefficients and subscripts to determine the number of each type of atom in a chemical formula or equation.

1. Launch: 11/13
 Grab your binder and immediately take a seat!
1. How many of each atom are in the following molecules:
i. Br2
ii. H2S
iii. CCl4
iv. H2SO4
v. C6H12O6

2. Announcements
 Binder checks are worth a decent number of
points!
 It is really important that you
 Do your launches
 Finish your homework (and get a stamp)
 Make-up all work from absences
 lpschem.wordpress.com

3. What are chemical
equations?
Mr. Heffner
11/13/09

5. What are chemical equations?
 A chemical equation is…
 a representation of a chemical reaction
2H2 + O2  2H2O
Reactants Products
• The substances that react • The substances that
• Left are produced (made)
• Right

6. What are chemical equations?
 A chemical equation is…
 a representation of a chemical reaction
2H2 + O2  2H2O
Reaction
Arrow
• “turns into”
• like an equals (=) sign

7. What are chemical equations?
 A chemical equation is…
 a representation of a chemical reaction
2H2 + O2  2H2O
Coefficients Subscripts
• Comes before the • Comes after the atom
compound • Sub = below
• distributed to all

8. Example
1. How many H atoms does 2H2 have?
 multiply the subscript and the coefficient
 Coefficient = 2
 Subscript = 2
 2 X 2 = 4 hydrogen atoms

9. Example
2. How many H atoms does 2H2O have?
 multiply the subscript and the coefficient
 Coefficient = 2
 Subscript = 2
 2 X 2 = 4 hydrogen atoms

10. Example
3. How many O atoms does 2H2O have?
 multiply the subscript and the coefficient
 Coefficient = 2
 Subscript = not there = 1
 2 X 1 = 2 oxygen atoms

11. Example
4. How many O atoms does Mg(OH)2 have?
 multiply the subscript and the coefficient
 Coefficient = not there = 1
 Subscript = 2
 1 X 2 = 2 oxygen atoms

12. Foldable
 Make foldable and define terms. Draw an
illustration if necessary.
1. Chemical equation
2. Reactants
3. Products
4. Coefficient
5. Subscript
6. Chemical reaction
7. Chemical bond
8. Molecule/compound

13. Practice Question
 Practice question handout

14. Exit Slip
1. What are chemical equations?
a. Representations of chemical reactions in which the
reactants are listed to the left of a reaction arrow.
b. Representations of chemical bonds in which 2
valence electrons are depicted by a straight line
c. Representations of chemical reactions in which the.
products are listed to the left of the reaction arrow.
d. A way to show how reaction arrows turn into
reactants.

15. Exit Slip
HC2H3O2 + NaHCO3  NaC2H3O2 + H2CO3
2. 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

16. Exit Slip
4Na + 4H2O  4NaOH + 2H2
3. Which of the following identifies the coefficient for
H2O in the above chemical equation?
a. 1
b. 2
c. 4
d. 8

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

18. Exit Slip
5. Which of the following identifies the correct
number of atoms in 3H2SO4?
a. 3 H atoms, 3 S atoms, 3 O atoms
b. 2 H atoms, 1 S atom, 4 O atoms
c. 6 H atoms, 3 S atoms, 4 O atoms
d. 6 H atoms, 3 S atom, 12 O atoms

19. Homework
 Finish practice question worksheet