AP Chem
Semester 2 Review
1. A solution prepared by mixing 10 mL of 1 M HCl and 10 mL of 1.2 M NaOH has
a pH of
(a) 0 (b) 1 (c) 7 (d) 13 (e) 14
2. All of the following reactions can be defined as Lewis acid-base reactions except
(a) Al(OH)3(s) + OH–(aq) Al(OH)4–(aq)
(b) Cl2(g) + H2O(l) HOCl(aq) + H+(aq) + Cl–(aq)
(c) SnCl4(s) + 2 Cl–(aq) SnCl62–(aq)
(d) NH4+(g) + NH2–(g) 2 NH3(g)
(e) H+(aq) + NH3(aq) NH4+(aq)
3. Which of the following represents a process in which a species is reduced?
(a) Ca(s) Ca2+(aq)
(b) Hg(l) Hg22+(aq)
(c) Fe2+(aq) Fe3+(aq)
(d) NO3- (aq) NO(g)
(e) SO32–(aq) SO42–(aq)
Cd2+(aq) + 2 e– Cd(s) Eº = –0.41 V
Cu+(aq) + e– Cu(s) Eº = +0.52 V
Ag+(aq) + e– Ag(s) Eº = +0.80 V
4. Based on the standard electrode potentials given above, which of the following is
the strongest reducing agent?
(a) Cd(s) (b) Cd2+(aq) (c) Cu(s) (d) Ag(s) (e) Ag+(aq)
…Cr2O72–(aq) + …HNO2(aq) + …H+(aq) …Cr3+(aq) + …NO3–(aq) + …H2O(l)
5. When the equation for the redox reaction represented above is balanced and all
coefficients are reduced to lowest whole-number terms, the coefficient for H2O(l) is
(a) 3 (b) 4 (c) 5 (d) 6 (e) 8
6. Which of the following equations represents the net reaction that occurs when
gaseous hydrofluoric acid reacts with solid silicon dioxide?
(a) 2 H+(aq) + 2 F–(aq) + SiO2(s) SiOF2(s) + H2O(l)
(b) 4 F–(aq) + SiO2(s) SiF4(g) + 2 O2–(aq)
(c) 4 HF(g) + SiO2(s) SiF4(g) + 2 H2O(l)
(d) 4 HF(g) + SiO2(s) Si(s) + 2 F2(g) + 2 H2O(l)
(e) 2 H2F(g) + Si2O2(s) 2 SiF(g) + 2 H2O(l)
7. The ionization constant for acetic acid is 1.8X10–5; that for hydrocyanic acid is
4X10–10. In 0.1 M solutions of sodium acetate and sodium cyanide, it is true that
(a) [H+] equals [OH–] in each solution
(b) [H+] exceeds [OH–] in each solution
(c) [H+] of the sodium acetate solution is less than that of the sodium cyanide
solution
(d) [OH–] of the sodium acetate solution is less than that of the sodium cyanide
solution
(e) [OH–] for the two solutions is the same
HCl, acetic, hydrocyanic, water, ammonia
8. Five acids are listed above in the order of decreasing acid strength. Which of the
following reactions must have an equilibrium constant with a value less than 1?
(a) HCl(aq) + CN–(aq) HCN(aq) + Cl–(aq)
(b) HCl(aq) + H2O(l) H3O+(aq) + Cl–(aq)
(c) HC2H3O2(aq) + OH– (aq) C2H3O2–(aq) + H2O(l)
(d) H2O(aq) + NH2–(aq) NH3(aq) + OH–(aq)
(e) HCN(aq) + C2H3O2–(aq) HC2H3O2(aq) + CN–(aq)
9. All of the following statements about the nitrogen family of elements are true
except:
(a) It contains both metals and nonmetals.
(b) The electronic configuration of the valence shell of the atom is ns2np3.
(c) The only oxidation states exhibited by members of this family are –3, 0, +3, +5.
(d) The atomic radii increase with increasing atomic number.
(e) The boiling points increase with increasing atomic number.
10. Which of the following salts forms a basic solution when dissolved in water?
(a) NaCl
(b) (NH4)2SO4
(c) CuSO4
(d) K2CO3
(e) NH4NO3
11. The table below summarizes the reactions of a certain unknown solution when
treated with bases.
Which of the following metallic ions could be present in the unknown solution?
Limited Amountof Reagent
Excess Reagent
I NaOH (aq) White precipitate
Precipitate dissolves
II NH3(aq)
White precipitate
White precipitate
(a) Ca2+ (aq)
(b) Zn2+ (aq)
(c) Ni2+ (aq)
(d) Al3+ (aq)
(e) Ag+ (aq)
12-16 refer to the following acids:
A. CO2 B. HF C. H2S D. HI E. HBrO3
12. Which acid will turn a limewater (Calcium hydroxide) solution cloudy when it is added through it?
13. The only strong acid of the 5 choices
14. The diprotic acid
15. The acid with sp hybridization on one of its atoms
16. The acid whose strongest intermolecular force is hydrogen bonding
17-21 refer to the following acids
A. HClO B. HClO2 C. HClO3 D. HClO4 E. HCl
17. The strong acid(s)
18. The weakest acid
19. The acid with chlorine in the +5 oxidation state
20. The acid that will precipitate a solution of silver nitrate.
21. The acid that is the strongest oxidizing agent of the choices.
22-26 refer to the following bases
A. NH3 B. NaOH C. Na2CO3 D. CaCO3 E. Na3PO4
22. This base is insoluble in water
23. This base is soluble in water and bubbles upon addition of acid
24. This base is the strongest of the choices
25. This base can neutralize the most equivalents of acid of the choices
26. This base can be told from the others by smell
27-29 refer to the following salts
A. NaNO3 B. KBr C. AgI D. Ca3(PO4)2 E. FeCO3
27. This salt will not precipitate any aqueous solution of other salts
28. This salt becomes more soluble upon addition of acid
29. This salt becomes more soluble upon addition of ammonia
30. Which of these compounds has chlorine in the same oxidation state as in the chloride ion?
A. SCl2 B. OCl2 C. HClO D. HClO4. E. ClO2
31. Which of these should be added to an aqueous mixture containing magnesium and barium nitrate in
order to precipitate the magnesium but not the barium?
A. NaCl B. NaOH C. Na2SO4 D. Na2CO3 E. Na2S
32. 3H2 + N2 = 2NH3 (This reaction is exothermic)
I. Decreasing temperature
II. Increasing pressure
III. Adding a catalyst
Which of the above inputs will increase the amount of ammonia at equilibrium?
A. I only
B. II only
C. I and II
D. III only
E. I, II, and III
33. Cu + HNO3 = Cu2+ + NO + H2O
Identify the reducing agent in the above equation.
A. Cu
B. HNO3
C. NO
D. H2O
E. Cu2+
34. Mg + Al3+ = Mg2+ + Al
How many grams of aluminum are produced when 6.02X1023 electrons are transferred in this reaction?
A. 27g B. 13.5g C. 9g D. 7.75g E. 4.5g
MC Answers:
1. B
2. B
3. D
4. A
5. B
6. C
7. D
8. E
9. E
10. D
11. D
12. A
13. D
14. C
15. A
16. B, E
17. D,E
18. A
19. C
20. E
21. D
22. D
23. C
24. B
25. E
26. A
27. A
28. D,E
29. C
30. A
31. B
32. C
33. A
34. C
FR:
1. A2(g) + D2(g) = 2AD(g)
At 300K this reaction has a Keq of 900.00.
A. Calculate Kp
B. If 20.00 moles of A2 and 20.00 moles of D2 are placed in a 2L container, calculate the pressure before
any reaction occurs
C. Calculate the pressure in the container when equilibrium is reached. Justify your answer with
detailed calculations.
D. Calculate the molar concentration of each species when equilibrium is established.
E. Calculate delta G for the reaction at 300K.
2. The Ka of HF is 7.2X10-4. 1.00L of .100M solution of HF is obtained.
A. Write the Ka expression for HF.
B. Find the pH of this solution.
C. .0500 mol of NaF are added to the solution. Find the new pH.
3. The Kb of NH3 is 1.8X10-5. 1.00L of 1.00M NH3 is obtained.
A. Write the Kb expression for NH3.
B. Find the pH of the solution.
C. Find [OH-] of the solution.
D. How many moles of NH4Cl should be added to the solution to give a pH of 10.00?
4. The Ksp of calcium carbonate is 3.36X10-9. Excess calcium carbonate is added to water.
A. Calculate the molar solubility of calcium carbonate.
B. Calcium chloride is added to the solution so that the concentration of calcium ion is 1.00M. Calculate
the concentration of carbonate.
C. What effect will adding acid to the original solution have on the concentration of calcium? Explain.
5. Electrochem, include eq.
A. A chemist wishes to create a voltaic cell that will produce the greatest voltage. Which system should
they choose?
Ag+ e- = Ag E = .8V
Cu2+ + 2 e- = Cu E = .34V
Zn2+ + 2e- = Zn E = -.76V
Mg2+ + 2e- = Mg E = -2.38V
B. Write the cell notation or this cell.
C. Calculate E for this cell.
D. Give two ways to increase the voltage of the cell.
E. Give two ways to increase the current of the cell.
6. Predicting reactions
For each of the following three reactions, write a balanced equation for the reaction in part (i) and answer
the question about the reaction in part (ii). In part (i), coefficients should be in terms of lowest whole
numbers. Assume that solutions are aqueous unless otherwise indicated. Represent substances in
solutions as ions if the substances are extensively ionized. Omit formulas for any ions or molecules that
are unchanged by the reaction. You may use the empty space at the bottom of the next page for scratch
work, but only equations that are written in the answer boxes provided will be scored.
(a) Solid magnesium hydroxide is added to a solution of hydrobromic acid.
(i) Balanced equation:
(ii) What volume, in mL, of 2.00 M hydrobromic acid is required to react completely with 0.10 mol of
solid magnesium hydroxide?
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(b) Excess hydrochloric acid is added to a solution of cobalt(II) nitrate to produce a coordination
complex.
(i) Balanced equation:
(ii) Which species in the reaction acts as a Lewis base?
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(c) A copper wire is dipped into a solution of silver(I) nitrate.
(i) Balanced equation:
(ii) Describe what is observed as the reaction proceeds.
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7. A chemist is studying acids and bases. They find that Kw for water at 25C is 1X10-14 and at 100C it is
1X10-12. They study the compound deuterium oxide, also called heavy water. They find that the
autoionization constant of D2O is 9X10-16 at 20C. An alien chemist studies ammonia. They find that the
autoionization constant is 1.8X10-12 at the standard temperature of their planet.
A. Based upon the information above which is a stronger bond, O-H or O-D? Explain.
B. What is the pH of neutral 100C water? Explain.
C. If we wanted Khw to reach the value 1X10-14 should we raise or lower the temperature of the D2O?
Explain in terms of thermodynamics and equilibrium.
D. A chemist titrates a weak base with DCl.
D. Do you predict that DCl is a stronger or weaker acid than HCl? Explain.
E. Assume that DCl is a strong acid in water. How would using DCl instead of HCl affect the results of
the titration of a solid weak base in order to find the molar mass of the base?
F. How would the Pkb results of the base be affected? Assume the pH meter treats D+ just like H+.
G. A chemist decides to use KOD instead of KOH for the titration of a weak acid. They use the molar
mass of KOH to calculate how much KOD to use in their titrant. Assuming that the chemist can make it
so that the KOD does not absorb water from the atmosphere, how will this affect the results of their
titration on
i. molar mass of a solid weak acid
ii. Pka of the acid
H. A chemist wants to measure which is stronger, HCl or DCl. They decide to measure the conductivity
of 1.00000M solutions of each. Should they measure in water, acid, or base? Explain.
I. A chemist wants to measure the strength of deuterated acetic acid. Should they use pH paper or a pH
meter? Explain.
J. A chemist wants to tell the difference between the following solutions. All they have is 4 very small
pieces of litmus paper, 3 very small pieces of universal paper, and a pH meter that only has enough
battery left to be used twice. If the chemist wants to tell the difference between these solutions, what
should they do? 1M NaOH, 1M HCl, 1M HC2H3O2, 1M HC3H5O2.
K. Copper acetate is used as shark repellent. If someone has the following solutions, how can they use
pH to know which is copper acetate? Cu(C2H3O2)2, Cu(NO3)2, CuSO4, CuCl2.
8. A metallic substance is analyzed by chemists. The substance is to be dissolved using electricity. The
chemists know that the metallic substance is an alloy of silver and copper. A 1.00g sample requires
19.3A of electricity operating for 100.00 seconds to dissolve the sample. The chemists dissolved this
sample in a vessel containing 50.000ml of water.
A. Should the chemists set up the electrochemical cell with the alloy as the cathode or as the anode?
B. One of the chemists says they can't do the experiment without a salt bridge. Is this true? Explain,
possibly with one or more diagram(s).
C. Using the data in the prompt find the percentage of silver in the sample.
D. The chemists want to recover the silver without getting copper. Can they do this electrochemically?
Explain.
E. The chemists want to recover the silver by precipitation. Give one anion that will precipitate silver
only, one that will precipitate both silver and copper, and one that will precipitate neither.
F. The chemists analyze the silver by precipitating it with a suitable anion. Assume they use a 1.000
molar solution of sodium (insert anion from part E here). How many milliliters of this solution are
required to precipitate all the silver ion in the alloy sample?
G. The chemists want to perform the experiment at lower voltage so they can use a battery. Predict the
effect that each of these will have on the voltage needed to dissolve the alloy.
i. adding a ligand that can coordinate the metal ions
ii. adding an anion that can precipitate the metal ions
iii. adding nitric acid to the vessel
Answers:
1.
A. Kp = Kc because Δn = 0
B. p = nRT/v n = 40 mol, R = .082Latm/molK, T =300K v = 2L, so P = 492 atm.
C. 246 atm.
D. 18.75M AD, .625 for A2 and D2
E. -14,227KJ
2.
A. [H+][F-]/[HF]
B. 1.57
C. 2.84
3.
A. [NH4+][OH-]/[NH3]
B. 11.63
C. 4.27X10-3M
4.
A. 4.8X10-5M
B. 3.36X10-9M
C. Increase because it removes carbonate ion
5.
A. Magnesium/silver
B. Mg|Mg2+||Ag+|Ag
C. 3.18V
D. Decrease [Mg2+], increase [Ag+]
E. Increase the size of the electrodes, bigger salt bridge, higher [Ag+]
6.
A. Mg(OH)2 + H+ = Mg2+ + H2O
ii. 50ml
B. Co2+ + 4Cl- = CoCl42ii. Chloride ion, ClC. Cu + 2Ag+ = Cu2+ + 2Ag
ii. The Cu metal disappears and the solution turns blue. A gray or silvery metal forms.
7.
A. O-D is stronger as the K is lower. With a stronger bond, fewer bonds will break.
B. Its pH is 6 because there will be an [H+] of 1X10-6 and an [OH-] of 1X10-6. Neutral isn’t pH 7, it’s equal
acid and base. At 25C neutrality is pH 7.
C. Raise the temp because the process is endothermic. Raising the temperature of a system undergoing
an endothermic process will promote the process.
D. Weaker acid. D tends to form stronger bonds than H.
E. No effect because it doesn’t shift the inflection point.
F. Think about B and HB+ vs B and DB+. D will have a higher affinity for B than H does, making B look
like a stronger base when it is with D+ compared to when it is in H+. Stronger base is lower Pkb.
G. i. The titrant solution is too dilute so more volume will be required, increasing the number of moles
of acid and decreasing the calculated molar mass.
ii. We will assume that the D from the KOD will have a higher affinity for conjugate base than the H
does. This makes the acid look weaker, so higher Pka.
H. They should measure in a solvent other than water where less HCl and DCl will ionize. This has to be
an acidic solvent because the acid from the solvent will suppress the ionization of the HCl and DCl
enough to measure a difference in their strengths.
I. The pH meter is much more accurate so use it.
J. Use the litmus to ID the NaOH, then use the universal to ID the HCl from the 3 acids. Test the two
organic acids with the meter to tell the difference.
K. The anions of the copper salts are all Lewis bases. Any that are the conjugate bases of weak acids are
also Bronsted-Lowry bases. Most are the conjugate bases of strong acids but the copper acetate has
acetate which is a weak base. So, the others should be neutral pH while the copper acetate is above 7.
8.
A. Anode to oxidize the metal
B. They can do the experiment in one cell since there is no reducing agent in solution to react with the
oxidizing agent. They can use an inert electrode and just reduce water to hydrogen at the other
electrode. Or, they can deposit the silver at the cathode as they oxidize the alloy. If they do the process
in a cell with 2 compartments they do need a salt bridge. Here’s a picture of an electrolytic cell in one
compartment:
The cell above is used to purify copper from an impure anode to a purer cathode.
C. 51.7% by mass, 38.7% by moles There are .00479 mol of Ag (.517g) and .0076 mol of Cu (.483g).
D. Yes because the silver can be reduced on to a cathode at a lower voltage than copper.
E. sulfate, chloride, bromide and iodide will precipitate silver only, many ions will do both such as
sulfide, hydroxide, phosphate, and carbonate. Nitrate will precipitate neither
F. 4.79ml of any solution where one anion binds one silver, such as chloride or iodide, half for sulfide
and sulfate, one third for phosphate.
G. i and ii should lower voltage by removing metal ion product, iii should also lower voltage by removing
the hydroxide that forms at the cathode, the nitrate can react with Cu, lowering voltage.