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2010 AP Chemistry Exam

2010 AP Chemistry Exam. Section 1 50% of exam 90 min 75 Multiple Choice Questions (without calculator and only a basic periodic table) Section 2 50% of exam 95 min Part A 60% of Section 2 55 min (with calculator, p. table, SRP, & formula pages) Part B 40% of Section 2 40 min

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2010 AP Chemistry Exam

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  1. 2010 AP Chemistry Exam

  2. Section 1 50% of exam 90 min 75 Multiple Choice Questions (without calculator and only a basic periodic table) Section 2 50% of exam 95 min Part A 60% of Section 2 55 min (with calculator, p. table, SRP, & formula pages) Part B 40% of Section 2 40 min (without calculator; with p.table, SRP, & formulas) AP Exam Format

  3. Part A Equilibrium Problem Other Problem* Other Problem* Part B Reactions (3 parts) Essay* Essay* Components of Section 2 *Laboratory question—may appear EITHER in Part A and involve quantitative analysis of laboratory-based data OR in Part B as an essay question based on a laboratory experiment

  4. 2010 FORMAT(95 minutes) Part A55 minutes (with calculator) % Sect.2 Score • Equilibrium Problem 20% • Other Problem* 20% • Other Problem* 20% Part B40 minutes (no calculator) % Sect.2 Score Reactions Question (3, with no choice) 10% • Essay Question* 15% • Essay Question* 15% *One of the other problems or essays will be based on laboratory.

  5. Section 1—Multiple Choice Strategy • Examine each question for a maximum of 30 seconds (on the average, some will take less time allowing more time for others). • Quickly determine the subject of the question. • By the end of the 30 seconds either: • Mark the correct answer. • Mark a “Y” next to the questions that you know how to work but need more time. • Mark an “N” next to the questions that you don’t have any idea how to work. • Force yourself to move through 20 questions each 10 minutes and all 75 questions in < 40 minutes.

  6. Section 1—Multiple Choice Strategy • Now make a second pass concentrating on the “Y” questions only. Do not spend any time on the “N” questions. If you don’t know the correct answer, see if some key piece of knowledge will allow you to eliminate 2 or 3 choices. If so, make an intelligent guess. Complete this pass in < 40 minutes. • Now make your third pass. Focus onlyon the “N” questions. Attempt to eliminate at least 2 choices. If you can, make an intelligent guess. If not, leave it blank. Any correct choices on this pass are bonus points. You only have 10 minutes, so make it count! • Before time expires, count the number of questions that you have answered (It should be at least 60).

  7. Section 2 Problem 1—Equilibrium • Read the entire question before doing any work. Items later in the problem may provide keys to earlier sections. • Problem 1 is always equilibrium. Look for key words and clues to determine which type (acid/base, buffer, precipitation or gaseous equilibrium). • acid/base Look for the words acidorbase,KaorKb, [H+],[OH-],or[H3O+]. Any of these indicate an acid/base problem. • buffer Look for the word buffer. Also, check for a weak acid and its conjugate base.

  8. Section 2 Problem 1—Equilibrium • precipitation Look forKspor the wordsolubility. • gaseous equilibrium Look for the phase symbol (g) on most of the reactants and products. • After determining the type of equilibrium, write a reaction if one is not provided. Use the general formulas given below: • Acid HA + H2O H3O+ +A-orH+ +A-. • Base A- + H2O HA +OH-(use actual formulas!) • Precipitation MA(s) + H2O M+(aq) +A- (aq) • Gases 2A(g) + 3B(g) A2B3(g)

  9. Section 2 Problem 1—Equilibrium • Write an equilibrium constant expression. Leave out solids and liquids. • Put in all the given quantities into the equilibrium constant expression and solve for the unknown allowing the units to direct the problem. THINK!

  10. Section 2 Problem 1—Equilibrium • Make sure that your work is clearly organized and labeled and round all answers to the correct number of significant figures. (Use an ICE chart) • When working with an acid/base equilibrium, remember that the concentrations of either the hydrogen or hydroxide ions can be determined from the pH value. pH = - log[H+]and[H+] = 10-pHor pOH = - log[OH-]and[OH-] = 10-pOH. Also, pH + pOH = 14. • When adding volumes of solutions, the original concentration of each reactant is lowered by the percent of dilution.

  11. Section 2 Problem 1—Equilibrium • When a strong acid or base is added to a buffer, a reaction occurs with the component of the buffer to try to completely neutralize the strong acid or base. • The basic component of the buffer will neutralize a strong acid to formmore of the acidic component of the buffer. • The acidic component of the buffer will neutralize a strong base to formmore of the basiccomponent of the buffer. • After the neutralization, the buffer system will shift to re-establish the equilibrium based on the new initial concentrations of the acidic and basic components.

  12. Section 2 Integrated Problems 2&3 • Read each problem all the way through before doing any work to get a global view of the problems. • Determine which type of problem each is. Problems from past exams have included thermodynamics, empirical formulas from combustion data, colligative properties, stoichiometry, kinetics, gas laws, and electrochem. • Quantitative lab problemshave includedspectrophotometry & Beer’s Law plot, calorimetry, analyzing titration curves, molar mass by vapor density or freezing point depression, kinetics of iodine clock reaction, and others.

  13. Section 2 Integrated Problems 2&3 • Remember that if you cannot solve an earlier part of the problem, you may still get some credit for a later section by showing how you could use the earlier answer in succeeding parts. • Use the formula reference page to find which mathematical relationship may be helpful in solving the problem.

  14. Problem 4—Predicting Reactions 3 reactions: • Majority of points earned for writing the correct balanced net ionic equation • 2 points for correct product formulas • 1 point for correct reactant formulas • 1 point for correctly balancing equation • 1 point for descriptive question about the reaction

  15. Sample Q 4. 2010 Examination • DIRECTIONS: For each of the following three reactions, in part (i) write a BALANCED equation and in part (ii) answer the question about the reaction. 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. These are net ionic equations!

  16. Problem 4—Predicting Reactions • Write the reactants as chemical symbols showing each reactant in net ionic form as follows: • Strong acids, bases, & soluble salts written as ions • Weak acids, bases, & insoluble salts written as molecules • Classify the reactions as: acid/base, redox, precipitation, organic combustion, or other. • Answer the chemistry related question as specifically and concisely as possible.

  17. Q 4. Example • Example: A strip of magnesium is added to a solution of silver nitrate • Mg + 2 Ag + Mg 2+ + 2 Ag • Which substance is oxidized in the reaction? • Magnesium metal (Mg)

  18. Sample for 2010: 4a. Solid potassium chlorate is strongly heated resulting in a change in the oxidation numbers of both chlorine and oxygen. • (i) 2 KClO3 2 KCl + 3 O2 (ii)What is the oxidation number of chlorine before and after the reaction? • Chlorine has an oxidation number of +5 in KClO3 and -1 in KCl

  19. Sample for 2010: 4b. Solid silver chloride is added to a solution of concentrated hydrochloric acid forming a complex ion. • (i) AgCl + Cl- [AgCl2 ]- (ii) Which species acts as a Lewis base in the reaction? Explain. • The chloride ion acts as a Lewis base in the reaction because it donates an electron pair in the reaction.

  20. Sample for 2010: 4c. A solution of ethanoic (acetic) acid is added to a solution of barium hydroxide. • (i) HC2H3O2 + OH- H2O + C2H3O2- (ii) Explain why a mixture of equal volumes of equimolar solutions of ethanoic acid and barium hydroxide is basic. • In the mixture there are initially twice as many moles of hydroxide ions as moles of acid; since they react in a 1:1 ratio, there is an excess of hydroxide ions, leading to the basic solution.

  21. Sample for 2010: 4d. Ammonia gas is bubbled into a solution of hydrofluoric acid. • (i) NH3 + HF  NH4+ + F- (ii) Identify a conjugate acid-base pair in the reaction. • NH3 (base) and NH4+ (acid) OR HF (acid) and F-(base).

  22. Sample for 2010: 4e. Zinc metal is placed in a solution of copper(II) sulfate. (i) Zn + Cu2+ Zn2+ + Cu (ii) Describe the change in color of the solution that occurs as the reaction proceeds. • The blue color of the solution due to the presence of the hydrated copper(II) ion fades as the copper(II) ion reacts and the colorless hydrated zinc(II) ion forms.

  23. Sample for 2010: 4f. Hydrogen phosphide (phosphine) gas is added to boron trichloride gas. • (i) PH3 + BCl3 H3PBCl3 (ii) Which species acts as a Lewis acid in the reaction? Explain. • BCl3 , because it accepts the non-bonded pair of electrons of the phosphorous atom in PH3

  24. Sample for 2010: 4g. A solution of nickel(II) bromide is added to a solution of potassium hydroxide. • (i)Ni2+ + 2 OH- Ni(OH)2 (ii) Identify the spectator ions in the reaction mixture. • Spectator ions are the bromide ion (Br-) and the potassium ion (K+)

  25. Sample for 2010: 4h. Hexane is combusted in air. • (i) 2 C6H14 + 19 O2 12 CO2 + 14 H2O (ii) When one molecule of hexane is completely combusted, how many molecules of products are formed? • 1 molecule of hexane produces 13 molecules of products

  26. Section 2 Essay Questions 5 & 6 • These questions typically have several, sometimes unrelated parts on key concepts in chemistry or focus on acquired lab skills. Examples of essays from past exams have included thermodynamics, kinetics, atomic structure, bonding, drawing Lewis dot structures, using formal charges, molecular shapes, hybridization, KMT, and electrochem. • Qualitative lab essayshave includedidentifying soluble salts, splint tests, reactions of oxides in water, preparing solutions, and others.

  27. Section 2 Essay Questions 5 & 6 • Be as specific as possible in your answers. Look for clues in the question as to what is really important. • Answer the question. State exactly what you are asked, not what you would like to answer. • Do not simply restate the problem. • If you are asked to compare the properties of two substances, make sure you discuss each substance. • Remember that you will be getting partial credit. Answer any part about which you have any knowledge.

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