All your work for this assignment is to be done on separate sheets of paper that are
stapled together before coming to class. Your work should be clearly written with each
step of math shown and proper units given. No late papers will be accepted. If an answer
asks for an explanation you must use proper grammar and complete sentences. Using the
text for definitions is fine, but use your own words to describe the chemistry. Remember,
working together is a good idea, but do not copy each other. Copied work will result in
zeroes for both students. Ask questions as the unit progresses, too.
Problem Set #4 – Chemical Reactions Introduction
Due Wednesday Jan 7th
Section 10-1: Reactions and Equations
1) Define a chemical reaction. Use the terms “reactant and product” and write at
least three sentences in your definition. Don’t give examples… just a definition.
2) Determine if the following are chemical or physical changes.
a. You crumple this problem set up.
b. You tear this problem set up.
c. You light this problem set on fire and it turns into a pile of ash.
d. You place a piece of calcium in a beaker of water.
e. You place a sponge in a beaker of water.
f. You strike a piece of lead with a hammer and the piece of metal bends.
g. The addition of a solution of lead (II) nitrate to a solution of sodium
phosphate to produce a solution of sodium nitrate and solid particles of
lead (II) phosphate.
h. You breathe in O2 gas and exhale CO2 gas…
3) Give three types of evidence that indicate a chemical reaction has taken place.
4) The mass of the reactants must equal the mass of the products in any chemical
change. Why?
5) Why does your car stop running when you run out of gas?
6) Glow sticks are actually two sticks in one… a thin glass tube rests inside the
larger exterior plastic tube. Inside the glass tube is one reactant. Outside the
small thin glass tube and inside the large plastic stick is the other reactant. When
you buy a glow stick at the 4th of July Parade the first thing you have to do is snap
the tube. What does snapping the tube do and how does this lead to a chemical
reaction?
7) When balancing a chemical reaction the subscripts in the formulas can NEVER be
changed. Why?
8) The reaction below is balanced, but there are only ten molecules of reactants
while there are twelve molecules of products. How can this be balanced?
C6H12 + 9 O2  6 CO2 + 6 H2O
9) What is the difference between a word equation and a chemical equation?
10) Which numbers in the following balanced reaction of aluminum and sulfuric acid
are coefficients and which are subscripts?
3 H2SO4+ 2 Al  Al2(SO4)3 + 3 H2
11) Write the word equation for the following balanced reactions:
a. 2 Mg (s) + O2 (g)  2 MgO (s)
b. HCl (aq) + NaOH (aq)  H2O (l) + NaCl (aq)
c. 2 NH4NO3 (s) 2 N2 (g) + O2 (g) + 4 H2O(g)
d. NaOH (aq)+ AgNO3 (aq)  AgOH (s) + NaNO3
12) Balance the following reactions – be sure to copy them correctly into your
problem set…
a. C2H6 (g) + O2 (g)  CO2 (g) + H2O (g)
b. NaCl (aq) + Pb(NO3)2 (aq)  NaNO3 (aq) + PbCl2 (s)
c. Ca (s) + H2O (l)  Ca(OH)2 + H2 (g)
d. Ca(HCO3)2 (s)  CaO (s) + CO2 (g) + H2O (g)
e. Cu (s) + S6 (g)  CuS (s)
13) When nitric acid (HNO3) is added to a solid piece of copper, a brown noxious gas
called nitrogen dioxide is produced along with hydrogen gas and a solution of
copper (II) nitrate.
a. Write the word equation for the statement above.
b. Write the unbalanced formula equation.
c. Count the atoms for each element as a reactant (make a table)
d. Count the atoms for each element as a product (make a table)
e. Balance the reaction
14) Write a balanced chemical reaction for the following word equations.
a. Potassium chlorate decomposes to form potassium chloride and oxygen.
b. Aqueous solutions of copper (II) nitrate and sodium hydroxide react to
form solid copper (II) hydroxide and a solution of sodium nitrate.
c. Diphosphorous tetrabromide reacts with fluorine gas to produce
diphosphorous tetrafluoride and liquid bromine.
d. Octane (C8H12) and oxygen react to produce carbon dioxide and water.
15) Why is being able to name compounds correctly so important in chemistry?
16) List the diatomic elements – give their names and molecular formulas.
Multiple Choice Section
17) This law states the mass of reactants has to be equal to the mass of the products.
a. The Law of Definite Proportions
b. The Law of Multiple Proportions
c. The Law of Conservation of Mass
d. The Law of Chemical Reactions
18) Which of the following is a chemical change?
a. Pouring a glass of milk
b. Adding chocolate syrup to the milk
c. Stirring the chocolate syrup into the milk
d. Letting the milk sit out overnight and waking up to find sour milk
19) Which of the following is NOT a chemical change?
a. Lighting a match
b. Lighting a Bunsen Burner
c. Ice in a beaker over the Bunsen burner turn into water
d. Adding pieces of calcium to the water in the beaker
20) What are the coefficients that will balance this reaction?
___ HCl (aq) + ___ Mg(OH)2 (aq)  ___ H2O (l) + ___MgCl2 (aq)
a. 1, 2 ,2, 1
b. 2, 1, 2, 1
c. 2, 2, 1, 1
21) What is the “x” in the following equation?
C5H12 + _x_ O2  5 CO2 + 6H2O
a. 4
b. 5.5
c. 16
d. 8
d. 2, 1, 1, 2
e. 10
22) According to the diagram on the right, which equation would
correctly represent the reaction?
a)
b)
c)
d)
e)
8X + 8Y 8Z
8X + 2Y 8Z
8 X + 16 Y  24 Z
X + 2Y 2Z
2X + Y 3Z
Y
ZZ
X
Section 10-2: Classifying Chemical Reactions
23) Balance and Identify these reactions
a. H2 (g) + N2 (g)  NH3 (g)
b. H2O (g)  H2 (g) + O2 (g)
c. H2 (g) + O2 (g)H2O (aq)
d. Na (s) + 2 HCl (aq)  H2 (g) + NaCl (aq)
24) Identify the Types of These Balanced Reactions
a. LiI (aq) + AgNO3(aq)LiNO3(aq)+ AgI (s)
b. Na (s) + AgNO3 (aq)  NaNO3 (aq) + Ag(s)
c. H2CO3 (aq)  H2O (l) + CO2 (g)
d. HCl (aq) + NaOH (aq)  NaCl (aq) + H2O(l)
e. Na2CO3(aq) + CaSO4(aq) Na2SO4(aq) + CaCO3(s)
f. 4H2O (l) + 3Fe(s)  Fe3O4 (s) + 4H2 (g)
g. 4 Al(s) + 3 O2 (g)  2 Al2O3 (g)
h. CH4 (g) + 2 O2 (g)  CO2 (g) + 2 H2O (g)
25) What reactant is always needed for a combustion reaction to take place? What are
the two products that are always produced in the complete combustion of an
organic fuel?
26) What three elements are produced in the decomposition of sodium sulfate?
27) What four elements are needed to run the synthesis reaction that forms the ionic
compound ammonium sulfate?
28) What does the activity series show? What is the rule of thumb that you should
remember when looking at the activity series?
29) Complete the Problem Solving Lab on page 288 in your text book
30) Use your activity series to determine which reactants will react:
a. Na (s) + HCl (aq)
b. Mg (s) + NaCl (aq)
c. Au (s) + FeCl3 (aq)
or
or
or
H2 (g) + NaCl (aq)
Na (s) + MgCl2 (aq)
Fe (s) + AuCl (aq)
Multiple Choice section
31) Which product is missing from this single replacement reaction?
Cu (s) + H2SO4 (aq)  CuSO4 (aq) + ???
a. H (g)
b. H2 (g)
c. CuO (s)
d. O2 (g)
e. CO2 (g)
32) Lead(IV) oxide changes to lead(II) oxide when heated. Which set of masses
could occur in this experiment?
2 PbO2 (s)  2 PbO (s) + O2 (g)
a) test tube
test tube + PbO2
test tube + PbO
19.0 g
18.7 g
18.0 g
b) test tube
test tube + PbO2
test tube + PbO
19.0 g
19.3 g
18.0 g
c) test tube
test tube + PbO2
test tube + PbO
19.0 g
22.0 g
21.8 g
d) test tube
test tube + PbO2
test tube + PbO
19.0 g
22.0 g
22.3 g
33) When an element is reduced, its atoms
a. gain protons.
d. lose protons.
b. gain electrons.
e. lose electrons.
c. increase in atomic number.
34) Which expression represents the oxidation of the copper(I) ion?
Cu+  Cu2+ + e–
Cu+ + e–  Cu0
Cu+ + e–  Cu2+
(A)
(B)
(C)
(D)
(E)
Cu  Cu+ + e–
Cu2+ + e–  Cu+
35) What species is reduced in this reaction: Cl2(g) + 2Br–(aq)  Br2(aq) + 2Cl–(aq)
(A)Cl–
(B)Cl2
(C)Br–
(D)Br2
Section 10-3: Reactions in Water
36) Explain why when an acid and a base react it is considered a neutralization
reaction.
37) What is the purpose of Net Ionic Reactions? Why can the spectator ions be
removed?
38) Write the net ionic reaction for the following systems:
a.
b.
c.
d.
e.
HCl (aq)+ NaOH (aq)  H2O (l) + NaCl (aq)
HBr (aq)+ LiOH (aq)  H2O (l) + LiBr (aq)
Mg(OH)2 (aq)+ H2SO4(aq)  2 H2O (l) + MgSO4 (aq)
What type of reaction are all these double replacement reactions?
What is the common thread that runs through all three reactions?
39) Write the balance chemical reaction for the reaction of a solution of lead (II)
nitrate reacting with a solution of sodium iodide. Write the net ionic reaction, too.
40) Design an experiment to test for the presence of heavy metal ions in a drinking
water supply. The heavy metal ions you will want to test for are lead, mercury,
and iron. Use your solubility table and your understanding of double replacement
reactions to design an series of easy reactions to run.
Single Replacement Reactions
41) Predict if these single replacement reactions will run based upon the activity series.
a. Ag (s) + Fe(NO3)3aq)
b. Fe (s) + AgNO3 (aq)
c. Al (s) + Cu(NO3)2 (aq)
42) Given the following data, write an activity series or the elements A, B and C.
Atoms of A react with ions of B
Atoms of A react with ions of C
Atoms of B do not react with ions of C
Atoms of B do not react with ions of A
Atoms of C react with ions of B
Atoms of C do not react with ions of A
Red-Ox Reactions
43) For every oxidation reaction there must be a reduction reaction. Why? Define
oxidation and reduction in your response.
44) What is the memorable phrase for Red-Ox reactions?
45) Determine if each ½ reaction below is oxidation or reduction.
Fe+2 (aq) + 2 e-  Fe (s)
Ca (s)  Ca+2 (aq) + 2eBr2 (g) + 2 e-  2Br-1 (aq)
46) Identify the reactant being oxidized in these Red-Ox reactions.
Ca + Cu+2  Ca +2 + Cu
Fe + 3Ag +1  Fe +3 + 3 Ag
2 Cl -1 + Br2  2 Br -1 + Cl2