11 18 How Are Equations Balanced Part Ii
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Transcript of 11 18 How Are Equations Balanced Part Ii
Launch: 11/18 Grab your binder and immediately take a seat!
Place homework (practice questions) on desk.
Balance the following equations showing all 3-steps in your work!
1. __Na + __Cl2 __NaCl
2. __CH4 + __O2 __CO2 + __H2
Announcements Quiz on Friday!
and every Friday until Winter Break
How are equations balanced? – Part II
Mr. Heffner 11/18/09
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
Example #1 Balance the equation,
N2 + H2 NH3
Step #1: Count the atoms on both sides
N2 + H2 NH3
Example #1
2 X N 2 X H 1 X N 3 X H
Unbalanced!
Step #2: Change coefficient & multiply out
N2 + H2 NH3
Example #1
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 #1
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 #1
6 X H
2
2 X N 6 X H
3
2 X N
Balanced!
Balancing Buffet Grab a menu and “order” your 100 point “dinner”
Appetizers = 5 points Entrees = 10 points
Desserts = 15 points
Write questions on a piece of binder paper
Balance the equation showing all of your work! 1. Count the atoms 2. Add a coefficient 3. Check tally (and repeat)
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
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.
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
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
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.
Homework Finish practice question worksheet