Big Idea 3: “Chemical Reactions” AP LEVEL ASSESSMENT
_____ / 20 pts
Name:_______________________________________________________
DUE: Mon 3/9
Section I: Section I of this assessment contains multiple-choice questions. Clearly circle the response that best satisfies the prompt giving only one answer to each
question. The use of the College Board provided periodic table and equations and constants sheet is advised. You may use the assessment or a separate sheet of paper that you
need not attach for notes or scratch work. Use your time effectively, working as quickly as you can without losing accuracy. Do not spend too much time on any one question. Go
on to other questions and come back to the ones you have not answered if you have time. It is not expected that everyone will know the answers to all of the multiple-choice
questions. Your total score on Section I is based only on the number of questions answered correctly. Points are not deducted for incorrect answers or unanswered questions.
Use the following solubility rules to answer questions 1-4.
-Salts containing halide anions are soluble except for those containing Ag+, Pb2+
and Hg22+.
-Salts containing carbonate anions are insoluble except for those containing alkali
metals or ammonium.
10. Based on the particulate drawing of the products for the reaction below, which
reactant is limiting for the following reaction and why?
2K3PO4(aq) + 3MgI2(aq) → Mg3(PO4)2 (s) + 6KI(aq)
1. In the solutions of iron (II) nitrate and sodium carbonate are mixed, what would be
the formula of the precipitate?
(A) Fe3CO3
(B) Fe2(CO3)3
(C)NaNO3
(D) No precipitate would form.
2. If solutions containing equal amounts of AgNO3 and KCl are mixed, what is the
identity of the spectator ions?
(A) Ag+, NO3 -, K+ and Cl (B)
Ag+ and Cl (C) K+ and Ag+
(D)
K+ and NO3 –
3. If equimolar solutions of Pb(NO3)2 and NaCl are mixed, which ion will not be present
in significant amounts in the resulting solution after equilibrium is established?
(A) Pb2+
(B)
NO3 +
(C) Na
(D)
Cl 4. Choose the correct net ionic equation representing the reaction that occurs when
solutions of potassium carbonate and copper (I) chloride are mixed.
(A) K2CO3 (aq) + 2CuCl(aq) → 2KCl(aq) + Cu2CO3 (s)
(B) K2CO3 (aq) + 2CuCl(aq) → 2KCl(s) + Cu2CO3 (aq)
(C) CO32- + 2Cu+ → Cu2CO3 (s)
(D) CO32- + Cu2+ → CuCO3 (s)
5. A strip of metal X is placed into a solution containing Y2+ ions and no reaction
occurs. When metal X is paced in a separate solution containing Z2+ ions, metal Z
starts to form on the strip. Which of the following choices organized the reduction
potentials for metals X, Y, and Z from greatest to least?
(A) X > Y > Z
(B)
Y>Z>X
(C) Z > X > Y
(D)
Y>X>Z
6. Which of the following is true for an endothermic reaction?
(A) The strength of the bonds in the products exceeds the strength of the bonds
in the reactants.
(B) The activation energy is always greater than the activation energy for an
exothermic reaction.
(C) Energy is released over the course of the reaction.
(D) A catalyst will increase the rate of the reaction by increasing the activation
energy.
7. In which of the following compounds is the oxidation number of chromium the
greatest?
(A) CrO42(B)
CrO
(C) Cr3+
(D)
Cr(s)
8. On an energy diagram, the energy of the activated complex is always?
(A) between the energy levels of the products and reactants
(B) above the energy level of the reactants, but below that of the products
(C) below the energy level of the reactants, but above that of the products
(D) above the energy levels of both the reactants and products
9. What is the mass ratio of fluorine to boron in a boron trifluoride molecule?
(A) 1.8 to 1
(B)
3.0 to 1
(C) 3.5 to 1
(D)
5.3 to 1
(A) The K3PO4, because there are no excess PO43- ions after reaction
(B) The MgI2, because there are excess Mg2+ cations remaining after the
reaction.
(C) The K3PO4, because it contains a cation that cannot form a precipitate.
(D) The MgI2, because it requires more of itself to create the products.
11. What is the mass of oxygen in 148 grams of calcium hydroxide?
(A) 24 grams
(B)
32 grams
(C) 48 grams
(D)
64 grams
12. An ion containing only oxygen and chlorine is 31% oxygen by mass. What is its
empirical formula?
(A) ClO (B)
ClO2 (C) ClO3
(D)
ClO4 –
Use the following information to answer questions 13 – 16.
When heated in a closed container in the presence of a catalyst,
potassium chlorate decomposes into potassium chloride and oxygen gas
via the following reaction:
2KClO3 (s) → 2KCl(s) + 3O2 (g)
13. If 12.25 g of potassium chlorate decomposes, how many grams of oxygen gas will
be generated?
(A) 1.60 g
(B)
3.20 g
(C) 4.80 g
(D)
18.37 g
14. Approximately how many liters of oxygen gas will be evolved at STP?
(A) 2.24 L
(B)
3.36 L
(C) 4.48 L
(D)
22.4 L
15. If the temperate of the gas is doubled while the volume is held constant, what will
happen to the pressure exerted by the gas and why?
(A) It will also double because the gas molecules will be moving faster
(B) It will also double because the gas molecules are exerting a greater force
on each other.
(C) It will be cut in half because the molecules will lose more energy when
colliding.
(D) It will increase by a factor of 4 because the kinetic energy will be four time
greater.
16. Whys is a catalyst present during the reaction?
(A) A catalyst is necessary for all decomposition reactions to occur
(B) A catalyst reduces the bond energy in the reactants, making them easier to
activate.
(C) A catalyst reduces the energy differential between the reactants and the
products.
(D) A catalyst lowers the activation energy of the overall reaction and speeds it
up.
17. A sample of a hydrate of CuSO4 with a mass of 250 grams was heated until all the
water was removed. The sample was then weighed and found to have a mass of
160 grams. What is the formula for the hydrate?
(A) CuSO4 • 10H2O
(B)
CuSO4 • 7H2O
(C) CuSO4 • 5H2O
(D)
CuSO4 • 2H2O
18.
___ CN - + ___ OH- → ___CNO - + ___ H2O + ___ e When the half reaction above is balanced, what is the coefficient for OH- if all the
coefficients are reduced to the lowest whole number?
(A) 1
(B)
2
(C) 3
(D)
4
19.
CaCO3 (s) + 2H+(aq) → Ca2+ (aq) + H2O(l) + CO2 (g)
If the reaction above took place at standard temperature and pressure and 150
grams of CaCO3(s) were consumed, what was the volume of CO2 (g) produced at
STP ?
(A) 11 L
(B)
22 L
(C) 34 L
(D)
45 L
20. A gaseous mixture at 25˚C contained 1 mol of CH4 and 2 mol of O2 and the
pressure was measured at 2 atm. The gases then underwent the reaction shown
below.
CH4 (g) + 2O2 (g) → 2H2O(g) + CO2 (g)
What was the pressure in the container after the reaction had gone to completion
and the temperature was allowed to return to 25˚C?
(A) 1 atm
(B)
2 atm
(C) 3 atm
(D)
4 atm
21. A hydrocarbon was found to be 20% hydrogen by weight. If 1 mol of the
hydrocarbon has a mass of 30 grams, what is its molecular formula?
(A) CH2
(B)
CH3
(C) C2H4
(D)
C2H6
22.
Cr2O72- + 6I - + 14 H+ → 2Cr3+ + 3I2 + 7H2O
Which of the following statements about the reaction given above is NOT true?
(A) The oxidation number of chromium changes from +6 to +3
(B) The oxidation number of iodine changes from - 1 to 0.
(C) The oxidation number of hydrogen changes from +1 to 0.
(D) The oxidation number of oxygen remains constant.
23. In which of the following molecules does hydrogen have an oxidation state of -1?
(A) H2O
(B)
NH3
(C) CaH2
(D)
CH4
24. Oxygen takes the oxidation state -1 in hydrogen peroxide, H2O2. The equation for
the decomposition of H2O2 is shown below:
2H2O2 (aq) → 2H2O(l) + O2 (g)
Which of the following statements about the reaction shown above is true?
(A) Oxygen is reduced, and hydrogen is oxidized
(B) Oxygen is oxidized, and hydrogen is reduced
(C) Oxygen is both oxidized and reduces
(D) Hydrogen is both oxidized and reduced.
25. Based on the reduction potential given below:
Cu2+ + 2e- → Cu
E0 = +0.3V
2+
Fe + 2e → Fe
E0 = -0.4V
What is the reaction potential for the following reaction?
Fe2+ + Cu → Fe + Cu2+
(A) -0.7 V
(B)
-0.1 V
(C) +0.1 V
(D)
+0.7 V
26. Based on the reduction potential given below:
Cu2+ + 2e- → Cu
E0 = +0.3V
Zn2+ + 2e- → Zn
E0 = -0.8V
Mn2+ + 2e- → Mn
E0 = -1.2V
Which of the following rations will be favored?
(A) Mn2+ +
Cu →
Mn + Cu2+
(B) Mn2+ +
Zn →
Mn + Zn2+
2+
(C) Zn
+
Cu → Zn + Cu2+
(D) Zn2+ +
Mn → Zn + <n2+
27. Molten AlCl3 is electrolyzed with a constant current of 5.00 amps over a period of
600.0 second. Which of the following expressions is equal to the maximum mass of
Al(s) that plates out? (1 faraday = 96,500 coulombs)
(A) (600) (5.00)
grams
(96,500) (3) (27.0)
(B) (600) (5.00) (3) (27.0)
(96,500)
(C) (600) (5.00) (27.0) grams
(96,500) (3)
(D) (96,500) (3) (27.0)
(600) (5.00)
grams
grams
Use the following information to answer questions 28 – 31.
A voltaic cell is created using the following half-cells
Cr3+ + 3e- → Cr
E0 = -0.41V
2+
Pb + 2e → Pb
E0 = -0.12V
The concentrations of the solutions in each half-cell are 1.0 M
28. Which of the following occurs at the cathode?
(A) Cr3+ is reduced to Cr(s)
(B)
(C) Cr(s) is oxidized to Cr3+
(D)
Pb2+ is reduced to Pb(s)
Pb(s) is oxidized to Pb2+
29. If the Cr3+ solution was replaced with a solution at a higher concentration, what
would happen to the E0 value for the cell?
(A) It would increase because of the presence of extra Cr3+ ions, which are able
to donate more electrons.
(B)It would increase because the reaction would become more favored.
(C)It would decrease because the addition of Cr3+ ions would drive the equation
to the left.
(D) It would decrease because the stoichiometric ratio of Cr3+ ions to Pb2+ ions
is less than 1 in the balanced reaction.
30. Which of the following best describes the activity in the salt bridge as the reaction
progresses?
(A) Electrons flow through the salt bridge from the Pb/Pb2+ half-cell to the
Cr/Cr3+ half-cell.
(B) Pb2+ flows to the Cr/Cr3+ half-cell, and Cr3+ flows to the Pb/Pb2+ half-cell.
(C) Na+ flows to the Cr/Cr3+ half-cell, and Cl - flows to the Pb/Pb2+ half-cell.
(D) Na+ flows to the Pb/Pb2+ half-cell, and Cl - flows to the Cr/Cr3+ half-cell.
31. Which of the following best describes the activity in the salt bridge as the reaction
progresses?
(A) Electrons flow through the salt bridge from the Pb/Pb2+ half-cell to the
Cr/Cr3+ half-cell.
(B) Pb2+ flows to the Cr/Cr3+ half-cell, and Cr3+ flows to the Pb/Pb2+ half-cell.
(C) Na+ flows to the Cr/Cr3+ half-cell, and Cl - flows to the Pb/Pb2+ half-cell.
(D) Na+ flows to the Pb/Pb2+ half-cell, and Cl - flows to the Cr/Cr3+ half-cell.
Section II: Section II of this assessment contains free response questions. You may use separate sheets of paper or the assessment to organize your answers or for scratch
work, but you must write your answers on a separate sheet of blank paper in order for each response. Only material written in such a fashion will be scored. Examples and
equations may be included in your responses where appropriate. For calculations, clearly show the method used and the steps involved in arriving at your answers. You must
show your work to receive credit for your answer. Pay attention to significant figures. Write clearly and legibly. Cross out any errors you make; erased or crossed-out work will not
be scored. Manage your time carefully. You may proceed freely from one question to the next but your work responses must be written in order.
31. (SFR) A gaseous hydrocarbon sample is completely burned in air, producing 1.80
liters of carbon dioxide at standard temperature and pressure and 2.16 grams of
water.
(a) What is the empirical formula for the hydrocarbon?
35. (LFR) A student preforms an experiment in which a bar of unknown metal M is
paced in a solution with the formula MNO3. The metal is then hooked up to a copper
bar in a solution of CuSO4 as shown below. A salt bridge of KCl links the cell
together.
(b) What was the mass of the hydrocarbon consumed?
(c) The hydrocarbon was initially contained in a closed1.00 liter vessel ata
temperature of 32˚C and a pressure of 760 millimeters of mercury.
What is the molecular formula of the hydrocarbon?
(d) Write the balanced equation for the combustion of the hydrocarbon.
32. (SFR) The table below shows three common forms of copper ore.
Ore #
Empirical
Percent by Mass
Formulas
Copper Sulfur Iron
1
Cu2S
?
?
0
2
?
34.6
34.9 30.5
3
?
55.6
28.1 16.3
The potential for each cell was tested a found to have a value +0.74 V. Separately,
when a bar of metal M is placed in the copper sulfate solution, solid copper starts to
form on the bar. When a bar of copper was placed in the MNO3 solution, no visible
reaction occurs.
(a) What is the percent by mass of copper in Cu2S?
(b) What is the empirical formula of ore #2?
(c) If a sample of ore #3 contains 11.0 grams of iron, how many grams of sulfur
does it contain?
(d) Cu can be extracted from Cu2S by the following process:
3Cu2S (s) + 3O2 (g) → 3 SO2 (g) + 6Cu (s)
If 3.84 grams of O2 are consumed in the process, how many grams of Cu are
produced?
33. (SFR)
2Mg (s) + 2CuSO4 (aq) + H2O (l) → 2MgSO4 (aq) + Cu2O (s) + H2 (g)
(a) If 1.46 grams of Mg(s) are added to 500 milliliters of a 0.200-molar solution of
CuSO4, what is the maximum molar yield of H2 (g).
The following gives some reduction potentials for copper:
Half-reaction
E0
Cu2+ + 2e- → Cu (s)
0.34 V
Cu2+ + e- → Cu+
0.15 V
Cu+
0.52 V
+
e-
→ Cu(s)
(a) Write the net ionic equation that takes place in the Cu/M cell.
(b) What is the standard reduction potential for metal M?
(b) When all of the limiting reagent has been consumed in (a), how many moles
of the other reactant (not water) remain?
(c) Which metal acted as the anode and which as the cathode? Justify your
answer.
(c) What is the mass of the Cu2O produced in (a)?
(d) On the diagram of the cell, indicate which way the electrons are flowing in the
wire. Additionally, indicate any ionic movement occurring in the salt bridge.
(Yes I will grade (d) based on what you draw on the diagram above)
(d) What is the value of [Mg2+] in the solution at the end of the experiment?
(Assume that the volume of the solution remains unchanged.)
34. (SFR) Two electrodes are inserted into a solution of nickel (II) fluoride and a
current of 2.20 A is run through them. A list of standard reduction potentials is as
follows:
Half-reaction
E0
O2 (g) + 4H+ + 4e- → H2O (l)
2e-
F2 (g) +
→
2H2O (l) +
2e-
2F→ H2 (g) +
Ni2+ + 2e- → Ni (s)
1.23 V
2.87 V
2OH-
-0.83 V
-0.25 V
(a) Write the net ionic equation that takes place during this reaction.
(b) Qualitatively describe what an observer would see taking place at each
electrode.
(c) Will the solution become acidic, basic, or remain neutral as the reaction
progresses?
(d) How long would it take to create 1.2 g of Ni (s) at the cathode?
(e) What would happen to the voltage of the reaction in the Cu/M cell if the
concentration of the CuSO4 increased while the concentration of the MNO3
remained constant? Justify your answer.