exam 1 - Version 157 Exam 1 mcdevitt (52365) 1 This...

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Unformatted text preview: Version 157 Exam 1 mcdevitt (52365) 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. There are 25 regular exam questions each worth 8 points apiece for a total of 200 points (100 001 10.0 points A photon whose wavelength is 300 nm has energy 1. 1 . 982 10- 30 J. 2. 6 . 626 10- 28 J. 3. 6 . 022 10 23 J. 4. 4 . 528 10 44 J. 5. 6 . 626 10- 34 J. 6. 6 . 626 10- 19 J. correct Explanation: 002 10.0 points Radio station KLBJ broadcasts at a frequency of 93 . 7 10 6 s- 1 . Determine the length of the waves that corresponds to this frequency. 1. 2 10- 8 m 2. 93.7 m 3. 2 nm 4. 3.20 m correct 5. 3.20 nm Explanation: 003 10.0 points According to the results of Einsteins photo- electric effect experiment 1. there is a threshold wavelength; at longer wavelengths, photoelectrons are pro- duced while at shorter wavelengths they are not. 2. there is a threshold temperature; at higher temperatures, photoelectrons are pro- duced while at lower temperatures they are not. 3. there is a threshold frequency; at higher frequency, photoelectrons are produced while at lower frequency they are not. correct 4. there is a threshold intensity; at higher intensity, photoelectrons are produced while at lower intensity they are not. Explanation: When electromagnetic radiation (light) of sufficient minimum energy strikes a metal cathode, electrons are knocked off its sur- face, travel to an anode, and form a current through a circuit. Two important observations were: 1) Electrons can be ejected only if the light is sufficiently energetic. Electron ejection is independent of time or intensity. The mini- mum energy varies by element. 2) The current increases with increasing intensity and is independent of color. Therefore, light is made up of photons, each having a particular amount of energy that can be transferred to an electron during a colli- sion. If the energy is equal to or greater than the amount needed to liberate the electron, it can escape to join the photoelectric current. Intensity is the number of photons hitting a surface per unit time. 004 10.0 points Write the ground-state electron configuration of Pb 2+ . 1. [Xe] 4 f 14 5 d 10 6 s 1 6 p 1 2. [Xe] 4 f 14 5 d 5 6 s 1 6 p 6 3. [Xe] 4 f 14 5 d 10 6 s 2 correct 4. [Xe] 4 f 14 5 d 5 6 s 2 6 p 5 5. [Xe] 4 f 14 5 d 10 6 p 2 Version 157 Exam 1 mcdevitt (52365) 2 Explanation: Write the electron configuration for the atom and then adjust for the charge of the ion. The Aufbau order of electron filling is 1 s , 2 s , 2 p , 3 s , 3 p , 4 s , 3 d , 4 p , 5 s , 4 d , 5 p , 6 s , 4 f , 5 d , 6 p , etc ....
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This note was uploaded on 04/16/2009 for the course CH 52365 taught by Professor Mcdevitt during the Spring '09 term at University of Texas at Austin.

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exam 1 - Version 157 Exam 1 mcdevitt (52365) 1 This...

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