Balancing EquationsChapter 11.1

Pages 324-329

Atom InventoriesWriting a correct chemical equation

and counting the number of atoms of each element is VERY important

SubscriptsIndicate the number of ATOMS in a

compoundNEVER changed in order to balance

an equation – this will change the substance itself

Atom InventoriesWriting a correct chemical equation

and counting the number of atoms of each element is VERY important

CoefficientsIndicate the number of ELEMENTS or

COMPOUNDS in a reactionCAN be changed to balance an

equationDetermines the molar ratio of

substances in a reaction

Atom InventoriesPractice

C6H12O6

Ca(OH)2

3H2O2

2Fe2(CO3)3

3CaNO3 + 2O2 Ca = 3; N = 3; O = 13

C = 6; H = 12; O = 6Ca = 1; O = 2; H = 2H = 6; O = 6

Fe = 4; C = 6; O = 18

Keeping Track of Atoms ActivityWork in groups of three and finish this

activity in the next 10 minutesYour group may ask me a total of two

questions during this time…use them wisely

To get credit for this activity, ALL group members must have their sheet checked and 100% correct by the end of the time

Begin now….

Keeping Track of Atoms Activity

20 minutes

18 minutes

16 minutes

14 minutes

12 minutes

10 minutes

8 minutes

6 minutes

4 minutes2 minuteTime’s Up!!

Balanced EquationsA chemical equation that shows the same number of atoms of each element on each side of the equation.

Based on the Law of Conservation of MatterMatter cannot be created or

destroyed, only changed

Balance EquationsNumber of atoms on the reactant side must equal the number of atoms on the product side

C + O2 CO2

C O O OO C

Balance EquationsNumber of atoms on the reactant side must equal the number of atoms on the product side

Cu + O2 CuO Not balanced! Add coefficients

2Cu + O2 2CuO Cu Cu

Cu

CuO O

O

O

Balancing EquationsSteps1) Determine the correct chemical

formulas for each substance.2) Write the skeleton (unbalanced)

equation.3) Do an atom inventory (count the

number of atoms on each side).*Count polyatomic ions as one

atom

Balancing EquationsSteps4) Use coefficients to get the number of atoms to equal on each side of the equation.5) Redo the atom inventory with the new coefficients.6) Make sure coefficients are in the lowest whole number ratio.

Examples…balance skeleton equations from the Chemical Reactions homework #6-10

Algebraic Balancing1) Assign letters to unknown

coefficients.2) Make a grid indicating the

appearance of an element in each substance of the equation. Use a whole number and the coefficient “letter” to indicate each appearance.

Algebraic Balancing3) Reduce each equation.4) Assume a=1.5) Solve for the coefficients. If there is

a fraction for a coefficient, multiply ALL coefficients by the denominator.6) Write the balanced equation.