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AP Chemistry 1st Semester Practice Exam Multiple Choice 1. What mass of Au is produced when 0.0500 mol of Au2S3 is reduced completely with excess H2? (A) 9.85g (B) 19.7g (C) 24.5g (D) 39.4g (E) 48.9g 2. Write the formula for the compound aluminum hydride a) Al(OH)3 b) AlH c) AlOH d) AlH3 e) Al2H3 3. How many significant digits are in the following measurement 0.045060 cm a) 3 b) 4 c) 5 d) 6 e) 7 4. When hafnium metal is heated in an atmosphere of chlorine gas, the product of the reaction is found to contain 62.2 percent Hf by mass and 37.4 percent Cl by mass. What is the empirical formula for this compound? (A) HfCl (B) HfCl2 (C) HfCl3 (D) HfCl4 (E) Hf2Cl3 5. What is the name of the compound Rb2S? a) rubidium sulfide b) dirubidium sulfide c) dirubidium monosulfide d) rubidium I sulfide e) rubidium II sulfide 6. The density of aluminum is 2.70 g/cm3. The volume of a solid piece of aluminum is 1.50 cm3. What is the mass? a) 1.50 g b) 1.80 g c) 2.70 g d) 4.05 g 7. The reaction of silver metal and dilute nitric acid proceeds according to the equation above. If 0.10 mole of powdered silver is added to 10 ml of 6.0-molar nitric acid, the number of moles of NO gas that can be formed is: 3Ag(s) + 4HNO3 3AgNO3 + NO(g) + 2H2O (A) 0.015 mole (B) 0.020 mole (C) 0.030 mole (D) 0.045 mole (E) 0.090 mole 8. A substance has an empirical formula of CH2. Its molar mass is determined in a separate experiment as 83.5. What is the most probable molecular formula for this compound? a) C2H2 b) C6H2 c) C4H2 d) CH12 e) C6H12 9. Propane gas, C3H8, burns in excess oxygen gas. When the equation for this reaction is correctly balanced and all coefficients are reduced to their lowest whole-number terms, the coefficient for O2 is: (a) 4 (b) 5 (c) 7(d) 10 (e) 22 10. The reaction of 11.9 g of CHCl3 with excess chlorine produced 12.6 g of CCl4, carbon tetrachloride from the reaction: 2CHCl3 + 2Cl2 ----> 2CCl4 + 2HCl What is the percent yield? a) 50% b) 87% c) 82% d) 35% e) None of these 11. Aqueous solutions of sodium sulfide and copper II chloride are mixed together. Which statement is correct? a) Cu2S will precipitate from solution b) No precipitate forms c) CuS will precipitate from solution d) NaCl will precipitate from solution e) No reaction will occur 12. The net ionic equation for the reaction that occurs during the titration of nitrous acid with sodium hydroxide is: (A) HNO2 + Na+ + OH- NaNO2 + H2O (B) HNO2 + NaOH Na+ + NO2- + H2O (C) H+ + OH- H2O (D) HNO2 + H2O NO2- + H3O+ (E) HNO2 + OH- NO2- + H2O 13. A sodium chloride solution would be classified as a a) semi-electrolyte b) weak electrolyte c) strong electrolyte d) nonelectrolyte 14. What is the final concentration of barium ions, Ba2+, in solution with 100 ml of 0.10 M BaCl2 is mixed with 100 ml of 0.05M H2SO4? (A) 0.00M (B) 0.012M (C) 0.025M (D) 0.075M (E) 0.10 M 15. For which of the following transitions does the light emitted have the longest wavelength? a) n=4 to n=3 b) n=4 to n=2 c) n=4 to n=1 d) n=3 to n=2 e) n=2 to n=1 16. Which of the following atoms or ions has 3 UNPAIRED electrons? a) N b) O c) Al d) S2- e) Zn2+ 17. One of the outermost electrons in a strontium atom in the ground state can be described by which of the following sets of four quantum numbers? (A) 5,2,0,1/2 (B) 5,1,1,1/2 (C) 5,1,0,1/2 (D) 5,0,1,1/2 (E) 5,0,0,1/2 18. Which of the following represents the ground state electron configuration of Mn+3 ion? (A) 1s22s22p63s23p63d4 (B) 1s22s22p63s23p63d54s2 (C) 1s22s22p63s23p63d24s2 (D) 1s22s22p63s23p63d84s2 19. Which of the following statements is FALSE? a) Ionization energies are always positive. b) For any atom with at least two electrons, the first ionization energy is always smaller than the second ionization energy. c) Electron affinities are usually negative. d) Electron affinities decrease steadily when going from left to right across the periodic table. e) All are true. 20. Which is the most electronegative element? (A) O (B) La (C) Rb (D) Mg (E) N 21. In the periodic table, as the atomic number increases from11 to 17, what happens to the atomic radius? (A) It remains constant. (B) It increases only. (C) It increases, then decreases. (D) It decreases only. (E) It decreases, then increases. 22. ____________ is the energy change associated with the addition of an electron to a gaseous atom. a) electron affinity b) ionization energy c) charge ratio d) electron strength 23. The Lewis dot structure of which of the following molecules shows only one unshared pair of valence electron? (A) Cl2 (B) N2 (C) NH3 (D) CCl4 (E) H2O2 24. Which of the following diatomic species contains 1 sigma (s) and 2 pi (p) bonds? (A) Li2 (B) B2 (C) N2 (D) O2 (E) F2 25. CH4(g) + 2 O2(g) CO2(g) + 2H2O(l) Ho = -889.1 kJ Hfo H2O(l) = -285.8 kJ Hfo CO2(g) = -393.3 kJ What is the standard heat of formation of methane, Hfo CH4(g), as calculated from the data above? (A) -210.0 kJ/mole (B) –107.5 kJ/mole (C) –75.8 kJ/mole (D) 75.8 kJ/mole (E) 210.0 kJ/mole 26. Which one of the following processes is endothermic? a) 2H2(g) + O2(g) ----> 2H2O(g) b) H2O(g) ----> H2O(l) c) CH4(g) + 2O2(g) ----> CO2(g) + 2H2O(g) d) H2O(s) -----> H2O(l) ANS: D 27. Which of the following is probably true for a solid solute with a highly endothermic heat of solution when dissolved in water? (A) The solid has a low lattice energy (B) As the solute dissolves, the temperature of the solution increases (C) The resulting solution is ideal (D) The solid is more soluble at higher temperatures (E) the solid has a high energy of hydration 28. Solid zinc oxide, ZnO, has a heat of formation of about -84 Kcal/mole. Select the correct statement for a reaction producing 162 grams of zinc oxide. a) 42 Kcal are absorbed b) 81 Kcal are absorbed c) 81 Kcal are released d) 168 Kcal are absorbed e) 168 Kcal are released 29. Relatively slow rates of chemical reaction are associated with which of the following? (A) The presence of a catalyst (B) High temperature (C) High concentration of reactants (D) Strong bonds in reactant molecules (E) Low activation energy Free-Response Step 1: Ce4+ + Mn2+ ---> Ce3+ + Mn3+ Step 2: Ce4+ + Mn3+ ---> Ce3+ + Mn4+ Step 3: Mn4+ + Tl+ ---> Tl3+ + Mn2+ The proposed steps for a catalyzed reaction between Ce4+ and Tl+ are represented above. The products of the overall catalyzed reaction are (A) Ce4+ and Tl+ (B) Ce3+ and Tl3+ (C) Ce3+ and Mn3+ (D) Ce3+ and Mn4+ (E) Tl3+ and Mn2+ 2 NO(g) + 2 H2(g) ---> N2(g) + 2 H2O(g) Experiments conducted to study the rate of the reaction represented by the equation above. Initial concentrations and rates of reaction are given in the table below. (a) (i) Determine the order for each of the reactants, NO and H2, from the data given and show your reasoning. (ii) Write the overall rate law for the reaction. (b) Calculate the value of the rate constant, k, for the reaction. Include units. (c) For experiment 2, calculate the concentration of NO remaining when exactly one-half of the original amount of H2 has been consumed. (d) The following sequence of elementary steps is a proposed mechanism for the reaction. I. NO + NO <===> N2O2 II. N2O2 + H2 ---> H2O + N2O III. N2O + H2 ---> N2 + H2O Based on the data present, which of the above is the rate-determining step? Show that the mechanism is consistent with: (i) the observed rate law for the reaction, and (ii) the overall stoichiometry of the reaction.
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