Name_____________________________
Period__________
The Law of Conservation of Mass states that the mass of all substances before a reaction
equals the mass of all substances after a reaction. In other words, the total atomic mass of the
reactants should equal the total atomic mass of the products---if the equation is balanced
properly. Add the states to each element or compound.
Example Mg + O2  MgO
Balanced 2Mg + O 2 _ 2MgO
Atomic Mass 2(24) + 2(16)  2(24+ 16)
48 + 32  48 + 38
80

80
Part I: Balance the following equations and using the periodic table, calculate atomic masses of
the reactants and products.
1.
FeO 
Fe +
O2
Mass____________________________________________________
2.
Zn +
HCl 
ZnCl2 +
H2
Mass____________________________________________________
A properly written chemical equation can summarize any chemical change and obey the
Law of Conservation of Mass.
Word equations are qualitative equations where the reactants and products in a chemical
reaction are represented by words. Word equations do not give us the quantities of
reactants or products formed; however, they are the first step to identify the known facts the reactants and products.
Formula equations represent the reactants and products by their symbols or formulas.
These equations should include symbols for physical states (g, l, s, aq).
Example: Solid sodium combines with chlorine gas to produce solid sodium chloride.
Word Eqn: sodium + chlorine gas  sodium chloride
Formula Eqn: Na (s) + Cl2 (g)  NaCl
(s)
BALANCING EQUATIONS PRACTICE
Directions: Practice writing the word equation and the formula equation for each question
below.
1. Solid sodium oxide is added to water at room temperature and forms sodium hydroxide.
Word Eqn: _______________________________________________________________________________
Formula Eqn: ___________________________________________________________________________
2. Solid aluminum metal reacts with aqueous zinc chloride to produce solid zinc metal and
aqueous aluminum chloride.
Word Eqn: _______________________________________________________________________________
Formula Eqn: ___________________________________________________________________________
3. Zinc reacts with aqueous hydrochloric acid to produce a solution of zinc chloride and
hydrogen gas.
Word Eqn: _______________________________________________________________________________
Formula Eqn: ___________________________________________________________________________
4. Solid iron (III) oxide and carbon monoxide produce solid iron and carbon dioxide gas.
Word Eqn: _______________________________________________________________________________
Formula Eqn: ___________________________________________________________________________
Part II: Using the word equation, write and balance the following:
1. calcium oxide + water  calcium hydroxide
____________________________________________________________________________
2. silver nitrate + nickel  nickel ( II ) nitrate + silver
____________________________________________________________________________
3. sodium hydroxide + hydrochloric acid  sodium chloride + water
____________________________________________________________________________
4. zinc + sulfur  zinc sulfide
____________________________________________________________________________
BALANCING EQUATIONS PRACTICE
Balance the following equations and include the states (use s for metals, aq for salts, acids,
bases and g for gases with parentheses).
1)
____BaCl2 + ____K2SO4  ____BaSo4 + ____KCl
2)
____CuSO4 + ____NaOH  ____Cu(OH)2 + ____Na2SO4
3)
____Al + ____O2  ____Al2O3
4)
____Ca + ____O2  ____CaO
5)
____Cu + ____AgNO3  ____Ag + ____Cu(NO3)2
6)
____Zn + ____AgNO3  ____Ag + ____Zn (NO3)2
7)
____MgBr2 + ____Cl2  ____MgCl2 + ____Br2
8)
____Zn + ____HCl  ____ZnCl2 + ____H2
9)
____NaOH + ____HCl  ____NaCl + ____H2O
10) ____AgNO3 + ____Ni  ____Ni(NO3) 2 + ____Ag
11) ____Zn + ____S  ____ZnS
12) ____CaO + ____H2O  ____Ca(OH) 2