AP Chemistry - Problem Drill 17: Chemical Reactions
Question No. 1 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
1. A chemical reaction is the process of bond forming and breaking between
atoms. All reactions can be classified into six types. What type is the following
reaction:
H2CO3 (aq) + Ca(OH)2 (aq)  CaCO3 (aq) + 2 H2O (l)?
Question
(A) Composition
(B) Decomposition
(C) Single Replacement
(D) Acid-base
A. Incorrect!
Composition is more than one compound forming one compound.
B. Incorrect!
Decomposition is one compound breaking apart into multiple compounds.
C. Incorrect!
Single displacement reactions involve a compound and an element as reactants.
Feedback
D. Correct!
This is the reaction of carbonic acid and calcium hydroxide. This is an acid and base
reacting to give a salt and water. It is an acid-base or neutralization reaction.
H2CO3 is an acid and Ca(OH)2 is a base. The products (CaCO3 and H2O) are a salt
and water. This is an acid-base reaction or neutralization reaction, a special type of
double displacement.
The correct answer is (D).
Solution
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved
Question No. 2 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
2. Most of the binary acid (HX or H2S) can be produced by their element gases (H2
and X2). Determine the type of reaction for the production of HCl gas from its
elements.
Question
(A) Single displacement
(B) Acid-base
(C) Composition
(D) Decomposition
A. Incorrect!
This reaction is H2 + Cl2  2HCl. The single displacement is A + BC  AC + B. The
production of HCl gas from its elements is not a single displacement type.
B. Incorrect!
Although HCl is a strong acid, there is no base to reaction with. This reaction is H 2
+ Cl2  2HCl. It is not a neutralization reaction or acid-base reaction with a general
form HA + BOH  AD + CB.
Feedback
C. Correct!
Good job! This reaction H2 + Cl2  2HCl is a composition reaction or synthesis
reaction with a general form of A + B  AB.
D. Incorrect!
This reaction is H2 + Cl2  2HCl. This is the reversed type of decomposition
reaction.
Write the balanced reaction and match the general form of a reaction type. This
reaction H2 + Cl2  2HCl is a composition reaction or synthesis reaction with a
general form of A + B  AB.
The correct answer is (C).
Solution
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved
Question No. 3 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
3. Reduction is a half-reaction in redox. It is defined as a decrease in oxidation
number with a gain of electrons. Which of the following is a reduction reaction?
I.
II.
Question
Sr2+ + 2 e-  Sr
2 Cl-  Cl2 + 2 e-
(A) I
(B) II
(C) I and II
(D) Neither I nor II
A. Correct!
Good job! Reduction reduces the charge by the gain of electrons. Strontium is
going from +2 to 0, which is a reduction in charge.
B. Incorrect!
Reduction reduces the charge. Chloride is going from -1 to 0, which is not
reduction.
Feedback
C. Incorrect!
Reduction reduces the charge. Although strontium is being reduced from +2 to 0,
the chloride is being oxidized from -1 to 0.
D. Incorrect!
Look closely—one of them is a reduction reaction.
Reduction is the gain of electrons to reduce the charge of the species. Strontium is
being reduced from +2 to 0.
The second half reaction is an oxidation reaction since the chlorine is being oxidized
to a higher charge (-1 to 0).
The correct answer is (A).
Solution
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved
Question No. 4 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
4. The knowledge of solubility rules is essential in predicting whether a reaction
might involve the formation of a precipitate, i.e. an insoluble compound. Which of
the following is insoluble in water?
Question
(A) NaOH
(B) K3PO4
(C) Ba(OH)2
(D) CaSO4
A. Incorrect!
Sodium is soluble with most anions.
B. Incorrect!
Potassium is soluble with most anions.
C. Incorrect!
Hydroxide is soluble with barium.
Feedback
D. Correct!
Sulfate is not soluble with calcium. Most sulfate compounds are soluble except:
Ag+, Pb2+, Ba2+, Sr2+, and Ca2+.
Use the solubility rules. Look up the anion and determine if it is soluble or insoluble
with the particular cation. All these choice are soluble except calcium sulfate.
The correct answer is (D).
Solution
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved
Question No. 5 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
5. Predicting products is a difficult task with some exceptions. One of them is the
double displacement reaction. What would the products of the following reaction
be?
CaCl2 (aq) + Na2SO4 (aq)  ?
Question
(A) CaSO4
(B) CaSO4
(C) CaSO4
(D) CaNa2
(aq) + 2 NaCl (aq)
(s) + 2 NaCl (aq)
(s) + Na2Cl2 (aq)
(aq) + Cl2SO4 (aq)
A. Incorrect!
You have the correct products, but one of them is insoluble. Exchange the two
cations and write out the state of each species.
B. Correct!
Good job! This is a double displacement reaction and calcium sulfate is not soluble.
Exchange the two cations and write out the state of each species.
Feedback
C. Incorrect!
Your formula for sodium chloride is incorrect. Exchange the two cations and write
out the state of each species.
D. Incorrect!
Do not combine two cations and two anions. Cations only bond to anions.
Exchange the two cations and write out the state of each species.
This is a double displacement reaction. The cation of the first compound combines
with the anion of the second to form an insoluble CaSO4. Ca is +2 and SO4 is -2 so
the compound is neutral as written.
The cation of the second combines with the anion of the first to form NaCl, which is
neutral as written.
Use solubility rules to determine if one is insoluble. NaCl is soluble, but CaSO 4 is
not.
The correct answer is (B).
Solution
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved
Question No. 6 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
6. Sodium hypochlorite is commonly known as liquid bleach. It emits oxygen when
it degrades with another byproduct NaCl. Write out the reaction and determine the
type of reaction.
Question
(A) 2NaClO(aq)  2NaCl(aq) + O2(g) … Single Displacement Reaction
(B) NaClO + O2  NaClO3 … Composition Reaction
(C) 2NaClO(aq)  2NaCl(aq) + O2(g) … Decomposition Reaction
(D) 2NaClO3  NaCl + O2 … Composition Reaction
A. Incorrect!
The reaction is correctly written and balanced. However, this is not a single
displacement reaction.
B. Incorrect!
The reaction emits oxygen. This means that one of the products is O2. Oxygen
should not be the reactant in this case.
Feedback
C. Correct!
Good job! The single reactant is NaClO and the two products are NaCl and O2. Write
it out and balance it. It is a decomposition reaction.
D. Incorrect!
The reactant is sodium hypochlorite (NaClO), not sodium chlorate (NaClO3).
The single reactant is NaClO and the two products are NaCl and O2. Write it out and
balance it. Specify the state of each species. It is a decomposition reaction.
2NaClO(aq)  2NaCl(aq) + O2(g) … Decomposition Reaction
The correct answer is (C).
Solution
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved
Question No. 7 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
7. Redox reactions are a family of reactions with the transfer of electrons between
species. Each redox has two half-reactions. Oxidation refers to the loss of electrons
while reduction refers to the gain of electrons. An example of an oxidation reaction
is?
Question
(A) Na+ + e-  Na
(B) Cu2+ + e-  Cu+
(C) Cu2+ + 2 e-  Cu
(D) Cu+  Cu2+ + eA. Incorrect!
Oxidation reactions have an increase in charge due to the loss of electrons. Sodium
is reduced from +1 to 0 - this is a reduction reaction.
B. Incorrect!
Oxidation reactions have an increase in charge due to the loss of electrons. Copper
is going from +2 to +1 - this is a reduction reaction.
Feedback
C. Incorrect!
Oxidation reactions have an increase in charge due to the loss of electrons. Copper
is going from +2 to 0 - this is a reduction reaction.
D. Correct!
Good job! Oxidation reactions have an increase in charge due to the loss of
electrons. Copper’s charge is going from +1 to +2 - this is an oxidation reaction.
Oxidation is the release of an electron with an increase in oxidation number (i.e.
higher charge). The above reactions are called “half reactions” because they only
show half of the story. The overall reactions must include both the reduction and
oxidation half reactions.
Cu+  Cu2+ + eThis half-reaction proceeds forward to a higher charge in loss of an electron. It is
an oxidation reaction.
The correct answer is (D).
Solution
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved
Question No. 8 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
8. There are six main types of reactions: Composition or Synthesis Reactions;
Decomposition Reactions; Single Displacement Reactions; Double Displacement
Reactions; Neutralization (Acid-Base) Reactions and Redox Reactions (Combustion).
What type of reaction is the following?
2 C2H6 + 7 O2  4 CO2 + 6 H2O
Question
(A) Composition
(B) Decomposition
(C) Double displacement
(D) Combustion
A. Incorrect!
Composition reactions combine more than one compound into one compound. This
is a typical combustion reaction of hydrocarbons – a reaction with oxygen gas to
generate carbon dioxide and water.
B. Incorrect!
Decomposition reactions have one compound breaking down into more than one
compound. This is a typical combustion reaction of hydrocarbons – a reaction with
oxygen gas to generate carbon dioxide and water.
Feedback
C. Incorrect!
Double displacement reactions involve two compounds switching anions. This is a
typical combustion reaction of hydrocarbons – a reaction with oxygen gas to
generate carbon dioxide and water.
D. Correct!
This is a combustion reaction because of the reaction with O2. It is also a redox as
oxygen is reduced from 0 to -2 and carbon is oxidized from -3 to +4. All
combustion reactions are redox.
This is a typical combustion reaction, also a redox. Oxygen is changing charge from
0 to -2 and carbon is changing charge from -3 to +4. This is an oxidation-reduction
reaction.
A typical combustion reaction of hydrocarbons reacts with O2 to give CO2 and H2O.
The correct answer is (D).
Solution
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved
Question No. 9 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
9. Which reaction below does NOT form a precipitate as a product when the two
ionic compounds are mixed in a solution?
Question
(A) Ba(NO3)2 + Na2SO4 
(B) KCl + AgNO3 
(C) Cu(NO3)2 + Na2S 
(D) Zn(NO3)2 + SnCl2 
A. Incorrect!
According to the solubility rule for SO42-, there are five cations that form
precipitates with the sulfate anion. The completed reaction is: Ba(NO3)2(aq) +
Na2SO4(aq)  BaSO4(s) + 2NaNO3(aq) with BaSO4 as a precipitate.
B. Incorrect!
According to the solubility rule for Cl-, only cations Ag+, Pb2+ and Hg22+ form
insoluble compounds with Cl-. The completed reaction is: KCl(aq) + AgNO3(aq) 
AgCl(s) + KNO3(aq). AgCl is a well known precipitate.
Feedback
C. Incorrect!
According to the solubility rule for S2-, all cations except group IA and IIA form
precipitates with S2-. The completed reaction is Cu(NO3)2(aq) + Na2S(aq)  CuS(s)
+ 2NaNO3(aq). CuS is a precipitate.
D. Correct!
Good job! This is the one with no precipitate formed as a product. All NO3compounds are soluble. The complete reaction is Zn(NO3)2(aq) + SnCl2(aq) 
Sn(NO3)2(aq) +ZnCl2(aq). There is no precipitate in this reaction.
Solubility rules are the key to solve many chemistry reaction problems. Try to learn
and master them.
Follow each anion’s solubility rule and identify the insolubility for each product
species. The first four reactions all have precipitates as products. The last one has
no precipitate.
This is the one with no precipitate formed as a product. All NO3- compounds are
soluble.
Zn(NO3)2(aq) + SnCl2(aq)  Sn(NO3)2(aq) +ZnCl2(aq). There is no precipitate in
this reaction.
Solution
The correct answer is (D).
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved
Question No. 10 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
10. Write out the reaction between hydrochloric acid and calcium metal with the
release of H2 gas. Also indicate the type of reaction.
Question
(A) 2HCl(aq) + Ca(s)  CaCl2(aq) + H2(g) … Single displacement
(B) 2HClO(aq) + Ca(s)  CaCl2(aq) + H2(g) + O2(g) … Double displacement
(C) 2HCl(aq) + Ca(s)  Ca(OH)2(aq) + Cl2(g) … Single displacement
(D) 2HCl(aq) + Ca(s)  CaCl2(aq) + H2(g) … Composition
A. Correct!
Good job! The HCl and Ca metal react to give H 2 and CaCl2. This is a typical single
displacement.
B. Incorrect!
Hydrochloric acid is HCl not HClO. It is also a wrong reaction.
Feedback
C. Incorrect!
This reaction does give H2 as a product, not Cl2, as stated in the problem
statement.
D. Incorrect!
The reaction is written correctly. However, this is not a composition reaction.
In a single displacement reaction (also called substitution reaction), one element is
being displaced from a compound by another element, with a general form:
A + BC  AC + B
The HCl and Ca metal react to give H2 and CaCl2. This is a typical single
displacement.
2HCl(aq) + Ca(s)  CaCl2(aq) + H2(g) … Single displacement
The correct answer is (A).
Solution
RapidLearningCenter.com
 Rapid Learning Inc. All Rights Reserved