AP Chemistry: types of reactions & solutions
Section 1: Multiple Choice
1) 30. milliliters of 1.0-molar NaHCO3 the resulting concentration of Na+ is
(A) 2.0 M
(B) 2.4 M
(C) 4.0 M
(D) 4.5 M When 70. milliliter of 3.0-molar Na2CO3 is added to
(E) 7.0 M
2) A student wishes to prepare 2.00 liters of 0.100-molar KIO3 (molecular weight 214 g/mol). The proper
procedure is to weigh out
(A) 42.8 grams of KIO3 and add 2.00 kilograms of H2O
(B) 42.8 grams of KIO3 and add H2O until the final homogeneous solution has a volume of 2.00 liters
(C) 21.4 grams of KIO3 and add H2O until the final homogeneous solution has a volume of 2.00 liters
(D) 42.8 grams of KIO3 and add 2.00 liters of H2O
(E) 21.4 grams fo KIO3 and add 2.00 liters of H2O
3) A 20.0-milliliter sample of 0.200-molar K2CO3 solution is added to 30.0 milliliters of 0.400-molar
Ba(NO3)2 solution. Barium carbonate precipitates. The concentration of barium ion, Ba2+, in solution after
reaction is
(A) 0.150 M
(B) 0.160 M
(C) 0.200 M
(D) 0.240 M
(E) 0.267 M
4) The weight of H2SO4 (molecular weight 98.1 g/mol) in 50.0 milliliters of a 6.00-molar solution is
(A) 3.10 grams
(B) 12.0 grams
(C) 29.4 grams
(D) 294 grams
(E) 300. grams
5) Given that a solution is 5 percent sucrose by mass, what additional information is necessary to calculate the
molarity of the solution?
I. The density of water
II. The density of the solution
III. The molar mass of sucrose
(A) I only
(B) II only
(C) III only
(D) I and III
(E) II and III
6) A yellow precipitate forms when 0.5 M NaI(aq) is added to a 0.5 M solution of which of the following ions?
A) Pb2+ (aq)
B) Zn2+ (aq)
C) CrO42¯ (aq)
D) SO42¯ (aq)
E) OH¯ (aq)
7) When 100 mL of 1.0 M Na3PO4 is mixed with 100 mL of 1.0 M AgNO3, a yellow precipitate forms and
[Ag+] becomes negligibly small. Which of the following is a correct listing of the ions remaining in solution in
order of increasing concentration?
A) [PO43¯] < [NO3¯] < [Na+]
B) [PO43¯] < [Na+] < [NO3¯]
C) [NO3¯] < [PO43¯] < [Na+]
D) [Na+] < [NO3¯] < [PO43¯]
E) [Na+] < [PO43¯] < [NO3¯]
8) The volume of distilled water that should be added to 10.0 mL of 6.00 M HCl(aq) in order to prepare a
0.500 M HCl(aq) solution is approximately
A) 50.0 mL
B) 60.0 mL
C) 100. mL
D) 110. mL
E) 120. mL
9) The net ionic equation for the reaction between silver carbonate and hydrochloric acid is
(A) Ag2CO3 + 2H+ + 2 Cl¯ ---> 2 AgCl + H2O + CO2
(B) 2Ag+ + CO32¯ + 2 H+ + 2 Cl¯ ---> 2 AgCl + H2O + CO2
(C) CO32¯ + 2 H+ ---> H2O + CO2
(D) Ag+ + Cl¯ ---> AgCl
(E) Ag2CO3 + 2H+ ---> 2Ag+ + H2CO3
10) 5 Fe2+ + MnO4¯ + 8 H+ <===> 5 Fe3+ + Mn2+ + 4H2O
In a titration experiment based on the equation above, 25.0 milliliters of an acidified Fe2+ solution requires 14.0
milliliters of standard 0.050-molar MnO4¯ solution to reach the equivalence point. The concentration of Fe2+ in
the original solution is
(A) 0.0010 M
(B) 0.0056 M
(C) 0.028 M
(D) 0.090 M
(E) 0.14 M
Section II: Free Response
FRQ #1
•
(a)
A 1.2516 gram sample of a mixture of CaCO3 and Na2SO4 was analyzed by dissolving the sample and
completely precipitating the Ca2+ as CaC2O4. The CaC2O4 was dissolved in sulfuric acid and the
resulting H2C2O4 was titrated with a standard KMnO4 solution.
Write the balanced equation for the titration reaction, shown unbalanced below:
MnO4- + H2C2O4 + H+  Mn2+ + CO2 + H2O
(i) Indicate which substance is the oxidizing agent and which substance is the reducing agent.
(b)
The titration of the H2C2O4 obtained required 35.62 milliliters of 0.1092 molar MnO4- solution.
Calculate the number of moles of H2C2O4 that reacted with the MnO4(c)
Calculate the number of moles of CaCO3 in the original sample.
(d)
Calculate the percentage by weight of CaCO3 in the original sample.
FRQ#2
•
Permanganate ion, MnO4-, oxidizes sulfite ions to sulfate ion. The manganese product depends upon the
pH of the reaction mixture. The mole ratio of oxidizing to reducing agent is two to five at pH 1 (acidic),
and is two to one at pH 13 (basic). For each of these cases, write a balanced equation for the reaction,
and indicate the oxidation state of the manganese in the product containing manganese.
FRQ#3
•
A 0.150 g sample of solid lead(II) nitrate is added to 125 mL of 0.100 M sodium iodide solution.
Assume no change in volume of the solution. The chemical reaction that takes place is represented by
the following equation:
Pb(NO3)2(s) + 2 NaI(aq)  PbI2(s) + 2NaNO3(aq)
(a)
compounds.
List an appropriate observation that provides evidence of a chemical reaction between the two
(b)
Calculate the number of moles of each reactant.
(c)
Identify the limiting reactant. Show calculations to support your identification.
(d)
Calculate the molar concentration of NO3–(aq) in the mixture after the reaction is complete.
FRQ #4
•
Answer the following questions about acetylsalicylic acid, the active ingredient in aspirin.
(a)
The amount of acetylsalicylic acid in a single aspirin tablet is 325 mg, yet the tablet has a mass
of 2.00 g. Calculate the mass percent of acetylsalicylic acid in the tablet.
(b)
A student dissolved 1.625 g of pure acetylsalicylic acid in distilled water and titrated the
resulting solution to the equivalence point using 88.43 mL of 0.102 M NaOH(aq). Assuming that acetylsalicylic
acid has only one ionizable hydrogen, calculate the molar mass of the acid.
FRQ#5
5 Fe2+(aq) + MnO4–(aq) + 8 H+(aq)  5 Fe3+(aq) + Mn2+(aq) + 4H2O(l)
•
•
The mass percent of iron in a soluble iron(II) compound is measured using a titration based on the
balanced equation above.
(a)
What is the oxidation number of manganese in the permanganate ion, MnO4–(aq)?
(b)
Identify the reducing agent in the reaction represented above. Explain your reasoning.
The mass of a sample of the iron(II) compound is carefully measured before the sample is dissolved in
distilled water. The resulting solution is acidified with H2SO4(aq). The solution is then titrated with
MnO4–(aq) until the end point is reached.
(c)
Describe the color change that occurs in the flask when the end point of the titration has been
reached. Explain why the color of the solution changes at the end point.
(d)
Let the variables g, M, and V be defined as follows:
g = the mass, in grams, of the sample of the iron(II) compound
M = the molarity of the MnO4–(aq) used as the titrant
V = the volume, in liters, of MnO4–(aq) added to reach the end
•
point
In terms of these variables, the number of moles of MnO4–(aq) added to reach the end point of the
titration is expressed as M x V. Using the variables defined above, the molar mass of iron (55.85 g mol1), and the coefficients in the balanced chemical equation, write the expression for each of the following
quantities
(i)
The number of moles of iron in the sample
(ii)
The mass of iron in the sample, in grams
(iii)
The mass percent of iron in the compound
(e)
What effect will adding too much titrant have on the experimentally determined value of the
mass percent of iron in the compound? Justify your answer.
Equations :
Equation #1
(a)
A sample of solid iron(III) oxide is reduced completely with solid carbon.
(i)
Balanced equation:
(ii)
What is the oxidation number of carbon before the reaction, and what is the oxidation number of
carbon after the reaction is complete
(b)
(c)
Equal volumes of equimolar solutions of ammonia and hydrochloric acid are combined.
(i)
Balanced equation:
(ii)
Indicate whether the resulting solution is acidic, basic, or neutral. Explain.
Solid mercury(II) oxide decomposes as it is heated in an open test tube in a fume hood.
(i)
Balanced equation:
(ii)
After the reaction is complete, is the mass of the material in the test tube greater than, less than,
or equal to the mass of the original sample? Explain.
Equation #2
(a) A small piece of sodium is placed in a beaker of distilled water.
(i)
Balanced equation:
(ii)
The reaction is exothermic, and sometimes small flames are observed as the sodium reacts with
the water. Identify the product of the reaction that burns to produce the flames
(b)
Hydrogen chloride gas is oxidized by oxygen gas.
(i)
Balanced equation:
(ii)
If three moles of hydrogen chloride gas and three moles of oxygen gas react as completely as
possible, which reactant, if any, is present in excess? Justify your answer.
(c)
Solid potassium oxide is added to water.
(i)
(ii)
Explain.
Balanced equation:
If a few drops of phenolphthalein are added to the resulting solution, what would be observed?