CHEMISTRY 1710 - Practice Exam #3 - SPRING 2013 Section 1 - This section of the exam is multiple choice. Choose the BEST answer from the choices which are given and write the letter for your choice in the space provided. PV = nrt R= 0.0821 P1V1 T1 P2V2 mrt M L atm mol K = PV = mrt M = PV = T2 drt P 1. To what temperature must a balloon, initially at 25 C and 2.00 L, be heated in order to have a volume of 6.00 L? A) 993 K B) 403 K C) 75 K D) 894 K 2. How many moles of CO are contained in a 5.00 L tank at 155 C and 2.80 atm? A) 0.399 moles B) 1.10 moles C) 2.51 moles D) 0.455 moles 3. What is the volume of 5.60 g of O2 at 7.78 atm and 415K? A) 1.53 L B) 565 L C) 24.5 L D) 0.766 L 4. Which of the following samples will have the greatest volume at STP? A) 22 g CO B) 22 g He C) 22 g O2 D) 22 g Cl2 5. Place the following gases in order of increasing density at STP. N2 NH3 N2O4 Ar A) N2O4 < Ar < N2 < NH3 B) Ar < N2O4 < N2 < NH3 C) NH3 < Ar < N2 < N2O4 D) NH3 < N2 < Ar < N2O4 6. The density of a gas is 1.43 g/l at STP. What is the gas? A) Cl2 B) S C) O2 D) Ne
7. A 0.465 g sample of an unknown gas occupies 245 ml at 298 K and 1.22 atm. What is the molar mass of the unknown compound? A) 26.3 g/mol B) 33.9 g/mol C) 12.2 g/mol D) 38.0 g/mol 8. A mixture of He, Ne and Ar has a pressure of 7.85 atm. If the Ne has a mole fraction of 0.47 and Ar has a mole fraction of 0.23, what is the pressure of He? A) 4.2 atm B) 3.7 atm C) 1.8 atm D) 2.4 atm 9. Which statement is TRUE about kinetic molecular theory? A) A single particle does not move in a straight line. B) The size of the particle is large compared to the volume. C) The collisions of particles with one another are completely elastic. D) The average kinetic energy of a particle is not proportional to the temperature 10. Which of the following statements is TRUE? A) Particles of different masses have the same average speed at a given temperature. B) The larger a molecule, the faster it will effuse. C) At very high pressures, a gas will occupy a larger volume than predicted by the ideal gas law. D) For a given gas, the lower the temperature, the faster it will effuse. 11. Which of the following signs on q and w represent a system that is doing work on the surroundings, as well as gaining heat from the surroundings? A) q = +, w = - B) q = -, w = + C) q = +, w = + D) q = -, w = - 12. Calculate the change internal energy (ΔE) for a system that is giving off 45.0 kj of heat and is performing 855 J of work on the surroundings. A) 44.1 kj B) -44.1 kj C) -45.9 kj D) 9.00 x 102 kj 13. A sample of copper absorbs 43.6 kj of heat, resulting in a temperature rise of 75.0 C, determine the mass (in kg) of the copper sample if the specific heat capacity of copper is 0.385 J/g C. A) 1.51 kg B) 6.62 kg C) 1.26 kg D) 7.94 kg
14. The specific heat capacity of liquid water is 4.18 J/g-K. How many joules of heat are needed to raise the temperature of 5.00 g of water from 25.1 C to 65.3 C? A) 48.1 J B) 840 J C) 1.89 10 3 J D) 2.08 10-2 J 15. Which of the following substances (with specific heat capacity provided) would show the greatest temperature change upon absorbing 100.0 J of heat? A) 10.0 g Fe, CFe = 0.449 J/g C B) 10.0 g H2O, CH2O = 4.18 J/g C C) 10.0 g ethanol, Cethanol = 2.42 J/g C D) 10.0 g Au, CAu = 0.128 J/g C 16. How much energy is evolved during the reaction of 48.7 g of Al, according to the reaction below? Assume that there is excess Fe2O3. Fe2O3(s) + 2 Al(s) Al2O3(s) + 2 Fe(s) ΔH rxn = -852 kj A) 415 kj B) 769 kj C) 241 kj D) 130 kj 17. Use the standard reaction enthalpies given below to determine ΔH rxn for the following reaction: 2 NO(g) + O2(g) 2 NO2(g) ΔH rxn =? Given: N2(g) + O2(g) 2 NO(g) ΔH rxn = +183 kj 1/2 N2(g) + O2(g) NO2(g) ΔH rxn = +33 kj A) -150. kj B) -117 kj C) -333 kj D) +115 kj 18. Choose the reaction that illustrates ΔH f for NaHCO3. A) Na(s) + H2(g) + C(s) + O2(g) NaHCO3 (s) B) Na+(aq) + HCO3-1 (aq) NaHCO3 (s) C) Na+(aq) + H2O (l) + CO2 (g) NaHCO3 (s) D) Na(s) + 1/2 H2(g) + C(s) + 3/2 O2(g) NaHCO3 (s)
19. Use the information provided to determine ΔH rxn for the following reaction: ΔH f (kj/mol) CH4(g) + 3 Cl2(g) CHCl3(l) + 3 HCl(g) ΔH rxn =? CH4(g) -75 CHCl3(l) -134 HCl(g) -92 A) -151 kj B) -335 kj C) +662 kj D) +117 kj 20. Calculate the wavelength (in nm) of the blue light emitted by a mercury lamp with a frequency of 6.88 1014 Hz. A) 229 nm B) 436 nm C) 206 nm D) 485 nm 21. Calculate the energy of the violet light emitted by a hydrogen atom with a wavelength of 410.1 nm. A) 4.85 10-19 J B) 2.06 10-19 J C) 1.23 10-19 J D) 8.13 10-19 J 22. What total energy (in kj) is contained in 1.0 mol of photons, all with a frequency of 2.75 1014 Hz? A) 182 kj B) 219 kj C) 110 kj D) 326 kj 23. What are the possible orbitals for n = 3? A) s, p B) s, p, d, f C) s D) s, p, d
24. Each of the following sets of quantum numbers is supposed to specify an orbital. Which of the following sets of quantum numbers contains an error? A) n = 2, l = 1, ml = -1 B) n = 4, l = 2, ml =0 C) n = 3, l =3, ml = -2 D) n = 1, l = 0, ml =0 25. Which of the following statements is TRUE? A) The principal quantum number (n) describes the shape of an orbital. B) The angular momentum quantum number (l) describes the the size and energy associated with an orbital. C) The magnetic quantum number (ml) describes the orientation of the orbital. D) An orbital is the path that an electron follows during its movement in an atom. 26. Calculate the frequency of light associated with the transition from n = 2 to n = 3 in the hydrogen atom. A) 2.19 1014 s-1 B) 5.59 1014 s-1 C) 4.57 1014 s-1 D) 1.79 1014 s-1 27. Which of the following quantum numbers describes the size and energy of an orbital? A) magnetic quantum number B) principal quantum number C) angular momentum quantum number D) spin quantum number 28. Give the set of four quantum numbers that could represent the last electron added (using the Aufbau principle) to the Cl atom. A) n = 3, l = 1, ml = 1, ms = +½ B) n = 3, l = 0, ml = 1, ms = -½ C) n = 3, l = 2, ml =1, ms = +½ D) n = 2, l = 1, ml = 1, ms = -½ 29. Give the ground state electron configuration for Se. A) [Ar]4s23d104p4 B) [Ar]4s24d104p4 C) [Ar]4s23d104p6 D) [Ar]4s23d10 30. How many electrons are in the outermost shell of the Ga3+ ion in its ground state? A) 2 B) 3 C) 6 D) 18
Help equations: q = m x Cs x T (reactants) ΔHºrxn = ΣnpΔHºf (products) - ΣnrΔHºf ν=c/λ E=hν E=hc/λ λ=h/mν E n = -2.18 x 10-18 J (1/n 2 ) (n=1,2,3,...) Δx Δv h/4π Δ E n = -2.18 x 10-18 J (1/n f 2-1/n i2 ) n = 1, 2, 3, 4,... l = 0, 1, 2,..., n-1 ml = -l,..., 0,..., +l ms = ±½ R= 0.0821 L-atm mol -1 K -1 NA = 6.022 x 10 23 mol -1 h = 6.626 x 10-34 J-s c = 2.998 x 10 8 m/sec 0ºC = 273.15 K
Section 2 - Follow the directions to solve each problem. 1. An unknown liquid is vaporized in a 273-mL flask by immersion in a water bath at 99 C. The barometric pressure is 753 torr. If the mass of the liquid retained in the flask is 1.362 g, what is its molar mass? a. Find the number of moles of gas present using the ideal gas law..009 moles b. Using the measured mass of the liquid, find its molar mass. 150 g/mol 2. A small quantity of hydrogen was prepared by the addition of hydrochloric acid to zinc. 195 ml of hydrogen was collected over water at 25 C and 753 torr. from the reaction. (Pwater = 24 torr at 25 C) a. Write the balanced chemical equation for the reaction of zinc metal with hydrochloric acid to yield zinc chloride and hydrogen gas. Zn (s) + 2 HCl (aq)----> ZnCl2 (aq) + H2 (g) b. Correcting for water vapor pressure, what was the pressure of the hydrogen gas collected? 729 torr c. Using the ideal gas equation, calculate the number of moles of hydrogen gas collected?.00764 moles d. How many grams of zinc were present in the original reaction?.500 g