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CHEM1300F11-Midterm-Answers-v1 - Fall 2011 Midterm exam...

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Fall 2011 Midterm exam Version 1 Answer Key 1. Which exam version are you writing (see the header above)? This question is not worth any marks, but no concessions will be made if you answer it incorrectly. a. Version 1 b. Version 2 2. The first law of thermodynamics a. is why heat travels from a hot body to a cold body. b. is a statement of Newton’s first law: force = mass × acceleration c. is a statement of the conservation of energy. d. defines chemical energy. e. defines the total energy of an object as the sum of its potential and kinetic energy. 3. The figure below represents the energy level diagram for the hydrogen atoms, and the arrows labeled a f are possible electron transitions. Rank the transitions that involve the absorption of a photon from shortest to longest wavelength. 4. Which one of the observations below leads to the conclusion that energy levels in atoms are quantized? a. Only specific frequencies of radiation are absorbed and emitted by an atom. b. Electrons can be ejected from a piece of metal by shining a light on the metal surface that has a frequency that must be above a specific minimum that is characteristic of the metal. c. No matter how much you heat them, metals do not emit high energy radiation, i.e. energy greater than that of visible light. d. Even if you increase the intensity of light focused on a metal, if the frequency of the light is below a certain minimum that is characteristic of the metal, no electrons are ejected from the metal. e. When alpha particles are projected onto a thin metal foil target, most go straight through the foil, some go through the foil but get scattered, and a small number are reflected back towards their source. 5. How many orbitals correspond to the fourth principal shell ( n = 4) of an atom? n = 1 n = 2 n = 3 n = 4 c d a b e f Energy
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Fall 2011 Midterm exam Version 1 Answer Key 6. C 60 , known as buckminsterfullerene or “bucky ball”, is a naturally -occurring form of carbon that is shaped like a soccer ball. In 1999 C 60 was shown to exhibit wave-particle duality when diffraction and interference patterns where observed when C 60 molecules were passed through single and multiple slits, respectively. What is the wavelength of a C 60 molecule (mass: 1.20×10 24 kg) moving with a velocity of 210 m/s?
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