Homework 1-solutions - kramer (jrk2286) Homework 1...

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Unformatted text preview: kramer (jrk2286) Homework 1 sutcliffe (90830) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Which of the following describes a chemical change? 1. gasoline burns in an engine correct 2. alcohol evaporates 3. water is heated from 0 C to 50 C 4. wood is carved Explanation: A chemical change occurs when one or more substances are consumed (at least partially), and one or more new substances are formed. 002 10.0 points What is the volume of a sample of helium that has a mass of 2 . 5 10- 3 g, and a density of . 17847 g / L? Correct answer: 14 . 008 mL. Explanation: m = 2 . 5 10- 3 g d = 0 . 17847 g / L d = m V V = m d = 2 . 5 10- 3 g . 17847 g / L 1000 mL L = 14 . 008 mL 003 10.0 points What is the nuclear composition of an atom of iodine-131? 1. 131 protons 2. 53 protons, 53 electrons 3. 78 protons, 53 neutrons 4. 53 protons, 78 neutrons correct Explanation: p + = 53 For A Z X , A = mass number = # p + + # n and Z = atomic number = # p + . # n = A- # p + = 131- 53 = 78 004 10.0 points How many hydrogen atoms appear in the for- mula of ammonium sulfate? 1. 6 atoms 2. 2 atoms 3. 4 atoms 4. 10 atoms 5. 8 atoms correct Explanation: The ammonium ion is NH + 4 and the sulfate ion is SO 2 4- . Two NH + 4 are needed to balance the charge on each SO 2- 4 . The formula is (NH 4 ) 2 SO 4 . 005 10.0 points Choose the pair of names and formulae that do not match. 1. SCl 4 : sulfur tetrachloride 2. SnCl 4 : tin(V) chloride correct 3. MgSO 4 : magnesium sulfate 4. N 2 O 3 : dinitrogen trioxide 5. KNO 3 : potassium nitrate Explanation: 006 10.0 points Which of the following is the molecular for- mula for heptane? kramer (jrk2286) Homework 1 sutcliffe (90830) 2 1. C 7 H 16 correct 2. C 6 H 14 3. C 7 H 14 4. C 7 H 12 5. C 6 H 12 Explanation: 007 10.0 points Calculate the energy of a photon of light with a wavelength of 0.57 km. 1. 3 . 5 10- 25 J 2. 3 . 5 10- 23 J 3. 3 . 8 10- 31 J 4. 5 . 3 10 8 J 5. 3 . 5 10- 22 J 6. 5 . 3 10 11 J 7. 3 . 8 10- 34 J 8. 3 . 5 10- 28 J correct 9. 530000 J Explanation: = 0.57 km Here we use the equation E = hc where h is Plancks constant (6.6262 10- 34 J s) and c is the speed of light (3.00 10 8 m/s). Here well also need to convert km into meters (recall that 1 km = 1 10 3 m): E = (6 . 6262 10- 34 J s)(3 . 00 10 8 m / s) . 57 km 1 . 00 10 3 m 1 km = 3 . 48747 10- 28 J 008 10.0 points We conduct an experiment by shining 500 nm light on potassium metal. This causes electrons to be emitted from the surface via the photoelectric effect. Now we change our source light to 450 nm at the same intensity level. Which of the following is the result from the 450 nm light source compared to the 500 nm source?...
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This note was uploaded on 02/12/2012 for the course CH 301 taught by Professor Fakhreddine/lyon during the Summer '07 term at University of Texas at Austin.

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Homework 1-solutions - kramer (jrk2286) Homework 1...

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