Chemistry--Unit 4: Chemical Reactions
Practice Problems
I. Describing Chemical Change
1) Write the balanced equation for the reaction between hydrogen and oxygen that
produces water.
2H2(g) + O2(g)  2H2O (l)
2) Write the balanced equation for the reaction that produces iron (II) sulfide from iron
and sulfur.
Fe(s) + S(s)  FeS(s)
3) Write the balanced equation representing the heating of magnesium carbonate to
produce solid magnesium oxide and carbon dioxide gas.
MgCO3(s)  MgO(s) + CO2(g)
4) Write a balanced equation for the production of HCl gas from its elements.
H2(g) + Cl2(g)  2HCl(g)
5) Write a sentence that completely describes the chemical reaction represented by this
balanced equation. 2HCl(aq) + CaCO3(s)  CO2(g) + CaCl2(aq) + H2O(l)
hydrochloric acid and solid calcium carbonate react to produce carbon dioxide, water,
and aqueous calcium chloride
6) Write a balanced equation representing the formation of aqueous sulfuric acid from
water and sulfur trioxide gas.
H2O(l) + SO3(g)  H2SO4(aq)
7) Write a balanced equation from this word equation.
aqueous silver nitrate + copper metal  silver metal + aqueous copper (II) nitrate
2AgNO3(aq) + Cu(s)  2Ag(s) + Cu(NO3)2(aq)
8) Write a balanced equation from this word equation.
phosphorus + oxygen  tetraphosphorus decoxide
4P(s) + 5O2(g)  P4O10(g)
II. Types of Chemical Reactions
9) Write a balanced equation representing the reaction of magnesium with oxygen to
produce magnesium oxide. What type of reaction is this?
2Cu(s) + O2(g)  2CuO(s)
combination
10) Write the balanced equation for the production of oxygen gas and sodium chloride
from the decomposition of sodium hypochlorite. What type of reaction is this?
2NaClO(aq)  2NaCl(aq) + O2(g)
decomposition
11) Write the balanced equation for the reaction between hydrochloric acid and calcium
metal. What type of reaction is this?
2HCl(aq) + Ca(s)  CaCl2(aq) + H2(g) single replacement
12) Write the balanced equation for the combustion of methane, natural gas (CH4) to
produce carbon dioxide and water vapor. What type of reaction is this?
CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)
combustion
Chemistry--Unit 4: Chemical Reactions
Practice Problems
13) Write the balanced equation for the reaction between iron (III) chloride and sodium
hydroxide. What type of reaction is this?
FeCl3(aq) + 3NaOH(aq)  Fe(OH)3(s) + 3NaCl(aq) double replacement
14) Using phosphoric acid and sodium hydroxide, write a balanced chemical reaction.
What type of reaction is this?
H3PO4(aq) + 3NaOH(aq)  Na3PO4 (aq) + 3H2O (or 3HOH) (l)
neutralization
15) Use the activity series of metals and nonmetals to predict whether the following
reactions will occur. Write balanced equations for those that do, “NR” for those that
do not.
a. Br2(l) + NaCl(aq)  NR (Br lower than Cl on the activity series of non-metals)
b. Ca(s) + Mg(NO3)2(aq)  Ca(NO3)2(aq) + Mg(s)
c. 2K(s) + H2SO4(aq)  K2SO4(aq) + H2(g)
d. Zn(s) + NaOH(aq)  NR (Zn lower than Na on the activity series of metals)
III. Reactions in Aqueous Solution
16) Write the net ionic equation for the reaction between aqueous barium nitrate,
Ba(NO3)2, and aqueous sodium sulfate, Na2SO4.
balanced: Ba(NO3)2(aq) + Na2SO4(aq)  2NaNO3(aq) + BaSO4(s)
complete: Ba+2 + NO3–1 + Na+1 + SO4–2  Na+1 + NO3–1 + BaSO4
net ionic: Ba+2(aq) + SO4–2(aq)  BaSO4(s)
17) Magnesium reacts with HCl to form hydrogen and magnesium chloride. Write the
balanced net ionic equation for this reaction.
balanced: Mg(s) + 2HCl(aq)  H2(g) + MgCl2(aq)
complete: Mg + H+1 + Cl–1  H2 + Mg+2 + Cl–1
net ionic: Mg(s) + 2H+1(aq)  H2(g) + Mg+2(aq)
18) The double-replacement reaction below results in the formation of the precipitate lead
chloride. Balance the equation and write the net ionic equation.
Pb(NO3)2(aq) + 2NH4Cl(aq)  PbCl2(s) + 2NH4NO3(aq)
net ionic: Pb+2(aq) + 2Cl–1(aq)  PbCl2(s)
19) Identify the precipitate formed when solutions of the following ionic compounds are
mixed. If no precipitate is formed, write “no precipitate”.
a. Zn(NO3)2 + SnCl2  no precipitate (both products, ZnCl2 and Sn(NO3)2, are
soluble)
b. KCl + AgNO3  AgCl(s) + KNO3(aq)
c. Cu(NO3)2 + Na2S  CuS(s) + 2NaNO3(aq)
d. Al2(SO4)3 + 3Mg(OH)2  2Al(OH)3(s) + 3MgSO4(aq)