Chapter 3- Equations and Stoichiometry
Balancing Chemical Equations
Chemical equations are used to convey both qualitative and quantitative info about a reaction.
Heptane burns in oxygen to produce carbon dioxide and water.
The law of conservation of mass warrants the balancing of the equation.
Balancing is done by assuring there are the same number of atoms of each type on each side of the arrow.
NEVER CHANGE SUBSCRIPTS TO BALANCE EQUATIONS. Do write correct formulas first
before balancing is done.
For now , balancing will be a trial and error process.
However, there are tips.
1) Balance metals first.
2) Balance any element that is only in one place on each side first.
3) Save H and O for last.
4) Count polyatomic ions as units.
5) The AP Exam will expect whole number coefficients. So use fractions first, then multiply each
coefficient by 2.
Ex 2: Write a balanced equation for the reaction between chlorous acid and solid cobalt (II) hydroxide to
produce water and aqueous cobalt (II) chlorite.
Assign- 3.1, 3, 5, 7, 8
Patterns of Chemical Reactivity
Combustion of a hydrocarbon
Combustion of an oxygenated fuel
Combustion of a reactive metal
Synthesis (Combination) between two elements
Synthesis between metal oxides and water
Synthesis between nonmetal oxides and water
Decomposition of a carbonate
Decomposition of chlorate
Decomposition of hydroxide
Decomposition of acid
Metathesis (Double replacement)
Assign- WS Predicting products.
Predicting products and Writing Equations
Predict the formulas of the product(s) and write a balanced equation for each of the following reactions.
1) NaCl(aq) + AgNO3(aq)
3) HIO (aq) + Ca(OH)2 (aq)
4) Na2O(s) + H2O(l)
5) C2H5OH + O2
6) CuSO4 (aq) + Zn (s)
7) HC2H3O2(aq) + Fe (s)
8) CuCO3 (s)
9) S8 (s) + O2 (g)
10) Ca(s) + O2 (g)
11) NaI(aq) + Pb(NO3)2(aq)
13) HNO2 (aq) + Fe(OH)3 (s)
14) Li2O(s) + H2O(l)
15) C4H10 (l)+ O2 (g)
16) NiSO4 (aq) + Fe (s)
17) HBr (aq) + Sn (s)
18) K2CO3 (s)
19) P4 (s) + O2 (g)
20) Mg(s) + O2 (g)