Download Balancing Chemical Equations Notes

6.5 Balancing Chemical Equations
A skeleton equation represents all chemicals by their symbols and by numbers. It is NOT
balanced. Skeleton equations and chemical equations are universal. They can be understood in
every language all over the world!
Word Equation
methane
+
oxygen
➡
water + carbon dioxide
CH4
+
O2
➡
H2O
Skeleton Equation
+
CO2
In a balanced chemical equation the reactants and the products contain equal numbers of
atoms of each type. (If the reactants have 4 O then the products will have 4 O atoms) This
follows the Law of Conservation of Mass.
Use these steps to balance an equation.
1.
Determine the correct formulas and write the skeleton equation:
Fe
2.
➜
O2
Fe3O4
Count the number of atoms of each element in the reactants and products. (Polyatomic
ions appearing unchanged on each side are counted as a single unit). (A table is easiest)
Type of Atom
Reactants
Products
Fe
1
3
O
2
4
3.
Balance the elements one at a time by using coefficients. The coefficient is a whole
number that appear in front of the formula in an equation. When no coefficient is
written, it is assumed to be 1.
3 Fe
4.
5.
+
+
➜
2 O2
Fe3O4
Always check to be sure that the equation is balanced.
Type of Atom
Reactants
Products
Fe
3
3
O
4
4
Make sure all coefficients are in the lowest possible ratio. (Reduce if possible)
Hints: Never add extra compounds
Never change formulas (subscripts)
If an element appears in only one compound on each side balance this one first. When
one of the products or reactants is a free element (only one type of atom) balance this
last.
1
TRY THESE:
1.
_____C2H6 + _____O2
---> _____H2O
+ _____CO2
2.
_____O2 + _____C6H12O6
---> _____H2O
+ _____CO2
3.
___Br2 + ___H2O + ___SO2
---> ___HBr
+ ___H2SO4
4.
_____KOH + _____H3PO4
---> _____K3PO4
+ _____H2O
5.
______Zn + ______HCl
---> ______ZnCl2
+ ______H2
6.
______KClO3
---> ______KCl
+ ______O2
7.
______S8 + ______F2
---> ______SF6
8.
______Fe + ______O2
---> ______Fe2O3
2