CHEM 200/202 Exam 2 October 18, Lab Section #:

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1 Name: Lab Section #: Please mark your answers on the scantron sheet using a #2 pencil and also mark your answers on the exam itself. Mark Test From A on your scantron. 1. A 4.25 L container is filled with equal moles of diethyl ether (C2H5)2O and hydrogen cyanide gas (HCN) at 298 K. Under these conditions it takes 82.5 minutes for moles of (C2H5)2O to effuse from the container. How long will it take for moles of the HCN to effuse from the container? (a) 28.9 min (b) 82.5 min (c) 49.8 min (d) 137. min (e) 79.2 min 2. At low to moderate pressures (< 300 atm), real gasses, such as CO2, exert a lower pressure than predicted by the ideal gas equation. What is the reason for this? (a) Such gases will condense to liquids at these pressures. (b) The volume occupied by the gas molecules becomes significant. (c) The ideal gas law can only be applied accurately to diatomic gases. (d) Attractive intermolecular forces between the gas molecules slow their movement. (e) The ideal gas law does not take into account the kinetic-molecular theory of gasses. 3. Which scenario will result in the greatest decrease in energy for the system? (a) The system releases 234 cal of heat and has 430 J of work done to it. (b) The system gains 904 J of heat and does 23.9 cal of work. (c) The system does 321 cal of work and loses 2.34 kj of heat. (d) The system has 1.09 kj of work done to it and loses 892 cal of heat. (e) The system gains cal of heat and does kj of work. 4. Which is not a requirement for a standard enthalpy of formation equation? (a) All reactants must be elements. (b) All products must be molecules. (c) Only one mole of product can be formed. (d) Products must be gases. (e) All reactants must be in their standard states. rate A rate B = M B M A 1 of 7

2 5. Solid strontium chloride (SrCl2) is added to an aqueous solution of silver nitrate, precipitating silver chloride. Given that the standard enthalpy of reaction ( H rxn ) is kj determine the standard heat of formation ( H f) for silver ions (Ag + (aq)). SrCl2(s) + 2Ag + (aq) + 2NO3 - (aq) Sr 2+ (aq) + 2AgCl(s) + 2NO3 - (aq) (a) kj/mol (b) kj/mol (c) kj/mol (d) kj/mol (e) kj/mol 6. Determine the enthalpy for the reaction of 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) given the reactions below: N2(g) + 3H2(g) 2NH3(g) Hrxn = kj ½N2(g) + ½O2(g) NO(g) Hrxn = kj 12H2O(g) 12H2(g) + 6O2(g) Hrxn = 2901 kj (a) -906 kj (b) kj (c) 2900 kj (d) kj (e) kj 7. Dissolving g of solid sodium hydroxide in 245 g of water in a calorimeter with a heat capacity of (0.732 J/K) causes the temperature of the solution and the calorimeter to increase by C. If the solution has a specific heat capacity of J/g K, determine the enthalpy change ( H) for this dissolution. (a) kj (b) kj (c) 15.4 kj (d) 44.0 kj (e) -295 kj 8. Which is not an example of the wave-particle duality; where a particle may act like wave, or a wave may act like a particle? (a) The diffraction patterns of electrons passing through aluminum crystals. (b) Blackbody radiation. (c) The refraction of a beam of light passing from air into water. (d) The photoelectric effect. (e) The line spectrum for the emission of light from a hydrogen atom. 2 of 7

3 9. The single electron on a Li 2+ (g) atom is excited to the n=7 orbital. When the electron falls to the n=3 orbital a photon of light is emitted by the atom. What is the wavelength of this photon of light? (a) 496 nm (b) 1005 nm (c) 112 nm (d) 91.2 nm (e) 4468 nm 10. Radiation can be used for chemical reactions, principally to break bonds between atoms. From the list below identify the bond with the highest energy that can be broken by a photon of khz frequency. (a) H-H: 432 kj/mol (b) F-F: 159 kj/mol (c) H-F: 565 kj/mol (d) C-H: 413 kj/mol (e) O-H: 467 kj/mol 11. A single atom is accelerated to a velocity of 1.5% the speed of light. At this speed the atom has a de Broglie wavelength of m. What is the atom in question? (a) Helium (He) (b) Lutetium (Lu) (c) Rhodium (Rh) (d) Hydrogen (H) (e) An atom cannot have a wavelength. 12. A sulfur atom has an atomic radius of 103 pm and a mass of g. If one of the electrons orbiting the sulfur atom is moving (±4.2%) m/s and the mass of an electron is kg, what is the minimum uncertainty in the position of the electron? (a) 59 pm (b) 740 pm (c) m (d) 410 pm (e) m x ( ) m ( ) u ( ) h 4π 13. Electrons can be ejected from titanium if the the metal is struck by a photon with a energy sufficient to overcome the work function ( ) of J. Which of the photons below would have sufficient energy to eject a photon from titanium? (a) An infrared photon with wavelength = 934 nm (b) A UV photon with wavelength = 245 nm (c) A X-ray photon with wavelength = 9.21 nm (d) Options (b) and (c) (e) Options (a), (b), and (c) 3 of 7

4 14. What is represented by the principle quantum number? (a) The number of electrons in the atomic orbital. (b) The direction of the atomic orbital. (c) The shape of the atomic orbital. (d) The energy level of the atomic orbital. (e) The spin of the electron in the atomic orbital. 15. Which orbital is represented in the image to the right? (a) 1s (b) 2p (c) 2d (d) 3d (e) 4f 16. "Each electron in an atom must have its own unique set of quantum numbers" is a statement of (a) the aufbau principle. (b) the Pauli exclusion principle. (c) Hund's rule. (d) the periodic law. (e) Heisenberg's principle. 17. In a single atom, what is the maximum number of electrons that can have quantum number n = 4? (a) 16 (b) 18 (c) 32 (d) 36 (e) None of these choices is correct. 18. Which of the following electron configurations is impossible? There is only one correct answer. (a) 1s 2 2s 2 2p 6 3s 2 3p 4 (b) 1s 2 2s 2 2p 5 3s 1 3p 4 (c) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 (d) 1s 2 2s 2 2p 6 3s 3 3p 4 (e) 1s 1 2s 2 2p 6 3s 2 3p Select the correct electron configuration for Cu (Z = 29). (a) [Ar]4s 2 3d 9 (b) [Ar]4s 1 3d 10 (c) [Ar]4s 2 4p 6 3d 3 (d) [Ar]4s 2 4d 9 (e) [Ar]5s 2 4d 9 4 of 7

5 20. The first ionization of Bi(g) can be accomplished by hitting the atom with a photon with a wavelength of 170. nm. What is the magnitude of the first ionization energy for bismuth? (a) 1402 kj/mol (b) 704 kj/mol (c) J/mol (d) J/mol (e) 532 kj/mol 21. Which one of the following equations correctly represents the process relating to the ionization energy of X? (a) X(s) X + (g) + e (b) X2(g) X + (g) + X (g) (c) X(g) + e X (g) (d) X (g) X(g) + e (e) X(g) X + (g) + e 22. When comparing the successive ionization energies of an element, an unusually large increase in the ionization energy is always seen when (a) the first valence electron is removed. (b) the second valence electron is removed. (c) the eighth electron of is removed. (d) the first core electron is removed. (e) the last valence electron is removed. 23. "Electrons added to atomic orbitals of the same energy will remain unpaired with parallel spins until the subshell is more than half-filled" is a statement of (a) the aufbau principle. (b) Hund's rule. (c) the Pauli exclusion principle. (d) the periodic law. (e) the singularity rule. 24. The atom and ions listed below are all isoelectric with the same noble gas. From this information determine which arrangement of relative radii is correct? (a) A 2 > B > C > D + > E 2+ (b) E 2+ > D + > C > B > A 2 (c) A 2 > B > C < D + < E 2+ (d) A 2 < B < C > D + > E 2+ (e) None of these choices is correct. 25. Which of the following ions is the optimal ionization state of selenium? (a) Se 6+ (b) Se 4+ (c) Se 2+ (d) Se 2 (e) Se 4 5 of 7

6 26. Elements with first ionization energies and electron affinities generally form cations. (a) low, very negative (b) high, positive or slightly negative (c) low, positive or slightly negative (d) high, very negative (e) None of these choices is generally correct. 27. Which of the following elements has the largest second ionization energy (IE2)? (a) Li (b) B (c) O (d) F (e) Na 28. What is the quantum number to the electron removed from an aluminum atom during the second ionization of the atom? (a) n = 3, l = 1, ml = -1, ms = +½ (b) n = 3, l = 2, ml = +1, ms = -½ (c) n = 3, l = 1, ml = 0, ms = +½ (d) n = 3, l = 0, ml = 0, ms = +½ (e) n = 3, l = 0, ml = 0, ms = -½ 29. In the electron configuration [Ar]4s 2 3d 10 4p 4, which are valence electrons? (a) all of the electrons after the [Ar] (b) only the 4s 2 electrons (c) only the 3d 10 electrons (d) only the 4p 4 electrons (e) both the 4s 2 and the 4p 4 electrons 30. An atom of arsenic (As) is in its ground electronic state. Which one of the following sets of quantum numbers does not apply to any of its electrons? (a) n = 2; l = 1; ml = -1; ms = +½ (b) n = 3; l = 0; ml = 0 ; ms = -½ (c) n = 3; l = 2; ml = -2; ms = -½ (d) n = 4; l = 0; ml = 0 ; ms = -½ (e) n = 4; l = 2; ml = 1 ; ms = +½ 6 of 7

7 The following problems are extra credit. You will not be penalized for wrong answers 31. A reaction is carried out where 8.23 g of nitrogen gas is combined with 6.55 g of oxygen gas to produce NO(g). This reaction is carried out in balloon, inside a calorimeter that contains 725 g of water at 28.7 C. If the reaction between has a yield of 82.7%, what will be the final temperature of the water in the calorimeter? Assume that the heat capacity of the calorimeter, balloon, and gasses are negligible. ch2o = J/g K N2(g) + O2(g) 2NO(g) Hrxn =180.6 kj (a) 27.5 C (b) 8.12 C (c) C (d) 38.9 C (e) 18.6 C 32. Identify the element from Period 2, which has the successive ionization energies tabulated below. (a) Li (b) B (c) O (d) Ne (e) None of these choices is correct. 7 of 7