SNC2D1
Date:__________________
Name:_____________________
L14: 6.3 Law of Conservation of Mass and 6.4 Balancing Chemical Equations
In a chemical reaction, one or more substances change into different substances. The atoms that make up
the reactants recombine to form new products (these can be elements and/or compounds).
IN YOUR LAB INVESTIGATION:
What did you find out about the mass of the reactants compared to the mass of products?
REACTION 1 (sealed container)
REACTION 2 (unsealed container)
In all balanced chemical reactions:
____________________________________________________
this means that
______________________________________________________________________
This is the ________________________________________
This can be represented by: Balanced Chemical Equations
This means there has to be the same number of atoms of each type in the reactants (left side) as in the products (right side).
Recall:
word equation
Skeleton chemical equation
To balance we need to get the same number of each element in the reactants as in the products.
1. First make a table with 3 columns and write each element in the first
column.
2. The second column is the total of each atom in the reactants.
3. The third column is the total of each atom in the products.
4. Now balance by multiplying each of the formulas by the appropriate
coefficient to balance each of the atoms.
5. Re-calculate the totals.
6. Repeat steps 4 and 5 until the
# reactants = # products for each element.
7. Reduce coefficients if necessary.
Short cut: If you notice a polyatomic ion that is unchanged in the reaction, you can balance it as a group.
________ chemical equation
Notes:
(s) represents solid, (g) represents gas; (l) represents liquid, and (aq) represents aqueous
“+”
means “and”
“”
means “produces” or “yields”
SNC2D1
Practice: For each word equation, first write the skeleton equation then balance and write the final balanced equation.
1. word equation:
potassium chlorate  potassium chloride + oxygen
skeleton equation:
balanced equation:
2. word equation:
copper + silver nitrate  copper (III) nitrate + silver
skeleton equation:
balanced equation:
3. word equation:
iron + oxygen  iron (III) oxide
skeleton equation:
balanced equation:
4. word equation: magnesium + nitric acid  hydrogen gas + magnesium nitrate
skeleton equation:
balanced equation:
5. word equation: propane + oxygen  carbon dioxide + water
skeleton equation:
balanced equation:
Homework: 6.3 Read p. 230-232, complete p.232 #2,5,6; and read p. 233-236, complete p.237 #2-7