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Practice Test 11 - AP Chemistry

20 questions. Answer them in any order, then submit to see your score and every explanation.

  1. A galvanic cell is assembled under standard conditions with the anode labeled as an Al(s)|Al3+^{3+}(aq) electrode and the cathode labeled as a Ag+^+(aq)|Ag(s) electrode. A student claims the overall cell reaction is spontaneous. Which statement correctly describes the sign of Ecell∘E^\circ_{\text{cell}} and spontaneity for the cell as labeled?
  2. A student adds solid zinc hydroxide, Zn(OH)2(s)\text{Zn(OH)}_2(s), to two beakers at the same temperature. Beaker A is buffered at pH 5 and Beaker B is buffered at pH 10. Ignoring complex-ion formation, which statement best compares the solubility of Zn(OH)2\text{Zn(OH)}_2 in the two beakers and explains why?
  3. A student prepares two buffers using the same weak acid/conjugate base pair, HF/F−\mathrm{HF/F^-}, in water. - Buffer A contains much more total HF\mathrm{HF} and F−\mathrm{F^-} (more concentrated overall) than Buffer B. - Both buffers are prepared so that the amounts of HF\mathrm{HF} and F−\mathrm{F^-} are equal within each buffer. The student adds the same small amount of strong base, NaOH(aq)\mathrm{NaOH(aq)}, to equal volumes of Buffer A and Buffer B. Which statement best compares the pH changes?
  4. A neutral atom has the electron configuration [Ar] 4s2 3d7[\mathrm{Ar}]\,4s^2\,3d^7. How many unpaired electrons are present in the 3d3d subshell in the ground state?
  5. A reaction occurs in a coffee-cup calorimeter and causes the temperature of the solution to decrease from 26.0∘C26.0^\circ\text{C} to 23.0∘C23.0^\circ\text{C}. The total heat capacity of the solution is Csoln=500 J / ∘CC_{\text{soln}}=500\,\text{J}\,/\,^\circ\text{C}. What is the heat transferred for the solution, qsolnq_{\text{soln}}?
  6. Two types of electromagnetic radiation are described: Radiation X has frequency 3.0×1014 s−13.0\times 10^{14}\ \text{s}^{-1}, and Radiation Y has frequency 6.0×1014 s−16.0\times 10^{14}\ \text{s}^{-1}. Which comparison is correct for single photons of X and Y?
  7. A student compares two separate beakers: Beaker 1 contains 0.10 M HCl(aq) and Beaker 2 contains 0.10 M CH3_3COOH(aq). Which particulate-level comparison is most accurate?
  8. An atom absorbs a photon and an electron is promoted from a lower energy level to a higher energy level. Which change in the absorbed photon would increase the energy gap that can be bridged by a single photon?
  9. A neutral atom has atomic number 20. Which of the following is the correct condensed electron configuration for this atom?
  10. A student dissolves ammonia, NH3_3(g), in water to form an aqueous solution. Which particulate-level description best represents the major solute-containing species present (relative amounts qualitatively) in the solution?
  11. The formation of ozone in the gas phase can be represented as 3O2(g)→2O3(g)3\text{O}_2(g) \rightarrow 2\text{O}_3(g). For this process, ΔH>0\Delta H > 0 and ΔS<0\Delta S < 0. Which statement best describes the thermodynamic favorability of the reaction as written?
  12. A calorimeter has a total heat capacity of C=250 J ∘C−1C = 250\ \text{J}\,^{\circ}\text{C}^{-1}. If the calorimeter releases q=−1.00×103 Jq = -1.00\times10^3\ \text{J} of heat, what is the temperature change, ΔT\Delta T, in ∘C^{\circ}\text{C}?
  13. A catalyst is added to a reaction whose uncatalyzed energy diagram is shown. Which change would be expected for the catalyzed pathway, relative to the uncatalyzed pathway?
  14. In the PCl3PCl_3 molecule, the phosphorus atom has a partial positive charge. What is the reason for this charge distribution?
  15. A 0.020 M0.020\,\text{M} solution of Ca(OH)2(aq)_2(aq) is prepared at 25∘C25^\circ\text{C}. Assuming complete dissociation, what is the pOH of the solution?
  16. A student observes that dissolving a solid in water is exothermic (ΔHsoln<0\Delta H_{\text{soln}} < 0). Additional evidence suggests that the solvent becomes more ordered around the solute (ΔSsoln<0\Delta S_{\text{soln}} < 0). At 25∘C25^\circ\text{C}, which statement best describes whether dissolution is thermodynamically favored?
  17. A student adds a few drops of food coloring (a polar molecular dye) to water and observes it spread throughout the beaker over time. Which particulate-level description best explains the spreading?
  18. A 1.00 L container is set up at constant temperature for the reaction H2(g)+I2(g)⇌2HI(g)\mathrm{H_2(g) + I_2(g) \rightleftharpoons 2HI(g)}. Initially, [H2]=0.40 M[\mathrm{H_2}] = 0.40\ \mathrm{M}, [I2]=0.40 M[\mathrm{I_2}] = 0.40\ \mathrm{M}, and [HI]=2.00 M[\mathrm{HI}] = 2.00\ \mathrm{M}. The equilibrium constant is Kc=4.00K_c = 4.00. Using an ICE table (assume only [HI][\mathrm{HI}] changes appreciably), what is [HI][\mathrm{HI}] at equilibrium?
  19. A nonreacting mixture contains 0.30 mol0.30\,\text{mol} CO2_2 and 0.70 mol0.70\,\text{mol} N2_2. What is the mole fraction of CO2_2 in the mixture?
  20. A sample of dry ice, CO2_2(s), is placed in an open container at room temperature and turns directly into CO2_2(g). Considering only the CO2_2 (system), what happens to entropy during this phase change?

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