{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

AP prac 2001 - l 1 00 CHEMISTRY Section II(Total time—90...

Info icon This preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 6
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: l . 1 00 CHEMISTRY Section II (Total time—90 minutes) Part A Time—40 minutes YOU MAY USE YOUR CALCULATOR FOR PART A. CLEARLY SHOW THE METHOD USED AND THE STEPS INVOLVED IN ARRIVING AT YOUR ANSWERS. It is to your advantage to do this, since you may obtain partial credit if you do and you will receive little or no credit if you do not. Attention should be paid to significant figures. Be sure to write all your answers to the questions on the lined pages following each question in the booklet with the pink cover. Do NOT write your answers on the green insert. Answer Question 1 below. The Section II score weighting for this question is 20 percent. 1. Answer the following questions relating to the solubility of the chlorides of silver and lead. (a) At 10°C, 8.9 x 10‘5 g of AgCl(s) will dissolve in 100. mL of water. (i) Write the equation for the dissociation of AgCl(s) in water. (ii) Calculate the solubility, in mol L", of AgCl(s) in water at 10°C. (iii) Calculate the value of the solubility-product constant, K for AgCl(s) at 10°C. Sp’ (b) At 25°C, the value of KSp for PbC12(s) is 1.6 x 10'5 and the value of Ksp for AgCl(s) is 1.8 x 10““). (i) If 60.0 mL of 0.0400 M NaCl(aq) is added to 60.0 mL of 0.0300 M Pb(N03)2(aq), will a precipitate form? Assume that volumes are additive. Show calculations to support your answer. (ii) Calculate the equilibrium value of [Pb2+(aq)] in 1.00 L of saturated PbClz solution to which 0.250 mole of NaCl(s) has been added. Assume that no volume change occurs. (iii) If 0.100 M NaCl(aq) is added slowly to a beaker containing both 0.120 M AgNO3(aq) and 0.150 M Pb(NO3)2(aq) at 25°C, which will precipitate first, AgCl(s) or PbC12(s)? Show calculations to support your answer. GO ON TO THE NEXT PAGE. V Answer EITHER Question 2 below OR Question 3 printed on page 8. Only one of these two questions will be graded. If you start both questions, be sure to cross out the question you do not want graded. The Section 11 score weighting for the question you choose is 20 percent. 2 NO(g) + 02(g) —-> 2 N02(g) AH° = —1 14.1 k], AS° = ~146.5 J K"1 2. The reaction represented above is one that contributes significantly to the formation of photochemical smog. (a) Calculate the quantity of heat released when 73.] g of NO(g) is converted to N02(g). (b) For the reaction at 25°C, the value of the standard free-energy change, AG°, is -70.4 H. (i) Calculate the value of the equilibrium constant, K for the reaction at 25°C. Eq’ (ii) Indicate whether the value of AG° would become more negative, less negative, or remain unchanged as the temperature is increased. Justify your answer. (c) Use the data in the table below to calculate the value of the standard molar entropy, S°, for 02(g) at 25°C. Standard Molar Entropy, S° (J K-1 mol‘l) (d) Use the data in the table below to calculate the bond energy, in H mol‘l, of the nitrogen-oxygen bond in N02 . Assume that the bonds in the N02 molecule are equivalent (i.e., they have the same energy). Bond Energy (kJ mol‘l) Nitrogen-oxygen bond in NO Oxygen—oxygen bond in 02 Nitrogen-oxygen bond in N02 GO ON TO THE NEXT PAGE. 3. 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) The elements contained in acetylsalicylic acid are hydrogen, carbon, and oxygen. The combustion of 3.000 g of the pure compound yields 1.200 g of water and 3.72 L of dry carbon dioxide, measured at 750. mm Hg and 25°C. Calculate the mass, in g, of each element in the 3.000 g sample. (c) 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. (d) A 2.00 x 103 mole sample of pure acetylsalicylic acid was dissolved in 15.00 mL of water and then titrated with 0.100 M NaOH(aq). The equivalence point was reached after 20.00 mL of the NaOH solution had been added. Using the data from the titration, shown in the table below, determine (i) the value of the acid dissociation constant, K, , for acetylsalicylic acid and (ii) the pH of the solution after a total volume of 25.00 mL of the NaOH solution had been added (assume that volumes are additive). Volume of 0.100 M NaOH Added (mL) STOP If you finish before time is called, you may check your work on this part only. Do not turn to the other part of the test until you are told to do so. a; CHEMISTRY Part B Time—50 minutes NO CALCULATORS MAY BE USED FOR PART B. Answer Question 4 below. The Section H score weighting for this question is 15 percent. 4. Write the formulas to show the reactants and the products for any FIVE of the laboratory situations described below. Answers to more than five choices will not be graded. In all cases, a reaction occurs. Assume that solutions are aqueous unless otherwise indicated. Represent substances in solution as ions if the substances are extensively ionized. Omit formulas for any ions or molecules that are unchanged by the reaction. You need not balance the equations. ‘ Example: A strip of magnesium is added to a solution of silver nitrate. (a) Sulfur dioxide gas is bubbled into distilled water. (b) A drop of potassium thiocyanate solution is added to a solution of iron(III) nitrate. (c) A piece of copper wire is placed in a solution of silver nitrate. (d) Solutions of potassium hydroxide and propanoic acid are mixed. (e) A solution of iron(II) chloride is added to an acidified solution of sodium dichromate. (f) Chlorine gas is bubbled through a solution of potassium bromide. (g) Solutions of strontium nitrate and sodium sulfate are mixed. (h) Powdered magnesium carbonate is heated strongly. GO ON TO THE NEXT PAGE. Your responses to the rest of the questions in this part of the examination will be graded on the basis of the accuracy and relevance of the information cited. Explanations should be clear and well organized. Examples and equations may be included in your responses where appropriate. Specific answers are preferable to broad, diffuse responses. Answer BOTH Question 5 below AND Question. 6 printed on page 11. Both of these questions will be graded. The Section 11 score weighting for these questions is 30 percent (15 percent each). Solution 1 Solution 2 Solution 3 Solution 4 Solution 5 0.10M 0.10M 0.10M 0.10M 0.10M Pb(NO3)2 NaCl KMnO4 C2H50H KC2H302 5. Answer the questions below that relate to the five aqueous solutions at 25°C shown above. (a) Which solution has the highest boiling point? Explain. (b) Which solution has the highest pH? Explain. (c) Identify a pair of the solutions that would produce a precipitate when mixed together. Write the formula of the precipitate. (d) Which solution could be used to oxidize the Cl‘(aq) ion? Identify the product of the oxidation. (e) Which solution would be the least effective conductor of electricity? Explain. GO ON TO THE NEXT PAGE. -1 o- 5i 3 I‘(aq) + 82082‘(aq) —> I3'(aq) + 2 SO42‘(aq) 6. Iodide ion, I‘(aq), reacts with peroxydisulfate ion, SzOsz“(aq), according to the equation above. Assume that the reaction goes to completion. (a) Identify the type of reaction (combustion, disproportionation, neutralization, oxidation-reduction, precipitation, etc.) represented by the equation above. Also, give the formula of another substance that could convert I'(aq) to I3‘(aq). (b) In an experiment, equal volumes of 0.0120 M I‘(aq) and 0.0040 M 82082'(aq) are mixed at 25°C. The concentration of I3‘(aq) over the following 80 minutes is shown in the graph below. 0 1o 20 30 40 50 60 7o 80 Time (minutes) (i) Indicate the time at which the reaction first reaches completion by marking an “X” on the curve above at the point that corresponds to this time. Explain your reasoning. (ii) Explain how to determine the instantaneous rate of formation of I3'(aq) at exactly 20 minutes. Draw on the graph above as part of your explanation. (c) Describe how to change the conditions of the experiment in part (b) to determine the order of the reaction with respect to I‘(aq) and with respect to 52082‘(aq). (d) State clearly how to use the information from the results of the experiments in part (c) to determine the value of the rate constant, k, for the reaction. (e) On the graph below (which shows the results of the initial experiment as a dashed curve), draw in a curve for the results you would predict if the initial experiment were to be carried out at 35°C rather than at 25°C. i i l ¢w%uu%u+nw%u+w—flflm%% 0 10 20 30 4o 50 60 70 80 Time (minutes) GO ON TO THE NEXT PAGE. Answer EITHER Question 7 below OR Question 8 printed on page 13. Only one of these two questions will be graded. If you start both questions, be sure to cross out the question you do not want graded. The Section 11 score weighting for the question you choose is 15 percent. Wire KNo3 Salt Brid e N , .. 1.0 M Ni(NO3)2 1.0 M Zn(NO3)2' 7. Answer the following questions that refer to the galvanic cell shown in the diagram above. (A table of standard reduction potentials is printed on the green insert and on page 4 of the booklet with the pink cover.) (a) Identify the anode of the cell and write the half-reaction that occurs there. (b) Write the net ionic equation for the overall reaction that occurs as the cell operates and calculate the value of the standard cell potential, 13;” . V (c) Indicate how the value of E cell would be affected if the concentration of Ni(NO3)2(aq) was changed from 1.0 M to 0.10 M and the concentration of Zn(NO3)2(aq) remained at 1.0 M. Justify your answer. (d) Specify whether the value of Kell for the cell reaction is less than 1, greater than 1, or equal to 1. Justify your answer. a " GO ON TO THE NEXT PAGE. as 8. Account for each of the following observations about pairs of substances. In your answers, use appropriate principles of chemical bonding and/or intermolecular forces. In each part, your answer must include references to both substances. (a) Even though NH3 and CH4 have similar molecular masses, NH3 has a much higher normal boiling point (—-33°C) than CH4 (—164°C). (b) At 25°C and 1.0 atm, ethane (C2H6) is a gas and hexane (C6H14) is a liquid. (c) Si melts at a much higher temperature ('1,410°C) than Cl2 (—lOl°C). (d) MgO melts at a much higher temperature (2,852°C) than NaF (993°C). END OF EXAMINATION IF YOU FINISH PART B OF SECTION II BEFORE TIME IS CALLED, YOU MAY RETURN TO PART A OF SECTION II IF YOU WISH, BUT YOU MAY NOT USE A CALCULATOR. THE FOLLOWING INSTRUCTIONS APPLY TO THE BACK COVER OF THE SECTION II BOOKLET. 0 CIRCLE THE NUMBERS OF THE FREE-RESPONSE QUESTIONS YOU ANSWERED AS REQUESTED ON THE BOTTOM OF THE BACK PAGE. 0 MAKE SURE YOU HAVE COMPLETED THE IDENTIFICATION INFORMATION AS REQUESTED ON THE BACK OF THE SECTION II BOOKLET. 0 CHECK TO SEE THAT YOUR AP NUMBER APPEARS IN THE BOX(ES) ON THE BACK COVER. 0 MAKE SURE YOU HAVE USED THE SAMESET OF AP NUMBER LABELS ON ALL AP EXAMINATIONS YOU HAVE TAKEN THIS YEAR. -13- ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern