142A_Exam1A_071511 - Chem 142 VERSION A Summer 2011 CHEM...

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Unformatted text preview: Chem 142 VERSION A Summer 2011 CHEM 142 - Exam 1 Version A !!! DO NOT OPEN THIS EXAM BOOK UNTIL TOLD TO DO SO BY THE INSTRUCTOR !!! Instructor: Dr. Kari Pederson NO GRAPHING CALCULATORS ALLOWED Date: Time: Friday, July 15 9:40-10:40am NO HEADPHONES ALLOWED (EARPLUGS ARE OK) Location: BAG 154 NO HATS WITH BRIMS ALLOWED ONLY CALCULATORS MAY BE USED AS CALCULATORS (you may not use your cellular phone as a calculator) !!! PLEASE READ THIS !!! Indicate all of the following on your scantron form or five points will be deducted from your exam score: First Name, Last Name, Student Number, Section, Exam Version YOUR FULL NAME: _______________________ first name ________________________ discussion section ________________________ last name ________________________ seat number YOUR SECTION/SEAT: EXAM 1 VERSION A Page 1 of 9 Chem 142 VERSION A Points Possible 24 40 16 20 -5 100 Score Summer 2011 Question 1-8 9-16 17-20 21 Scantron Info? TOTAL EXAM 1 VERSION A Page 2 of 9 Chem 142 VERSION A Summer 2011 MULTIPLE CHOICE: CONCEPTS. 8 @ 3 pts each 24 POINTS TOTAL Please mark the one correct answer for each of the following questions on your scantron. 1. Which of the following is a chemical property of the element cesium? A) Cesium will react explosively if placed in water. B) Cesium is a soft metal that can be cut easily. C) Cesium, like other metals, conducts electricity. D) Cesium has a much smaller density than lead. E) Cesium is grayish in color. Which metric prefix symbol means 1 x 103? A) p B) m C) M D) k E) n As chemists and other scientists seek to understand the principles that govern nature they employ what is called the scientific method. The first step in this method is ____. A) the proposal of a hypothesis B) the testing of a scientific law C) the application for a research grant D) the testing of a hypothesis E) the making of observations Sodium metal reacts vigorously with water, releasing hydrogen gas as one of the products. A piece of sodium weighing 34.0 g was added to a beaker containing 76.0 g of water. The resulting solution weighed 98.0 g. How many grams of hydrogen gas were produced (assume no hydrogen gas remains in solution)? A) 12.0 g B) 22.0 g C) 32.0 g D) 42.0 g E) none of the above Of the following, only _______________ would be classified as a pure substance. A) beer B) water from the drinking fountain C) carbon dioxide D) salted popcorn E) skim milk 2. 3. 4. 5. EXAM 1 VERSION A Page 3 of 9 Chem 142 6. VERSION A Summer 2011 Which statement best describes ions? A) atoms in the same vertical group B) atoms with the same number of protons and electrons and different numbers of neutrons C) atoms with the same number of neutrons and electrons and different numbers of protons D) atoms with the same numbers of protons and neutrons and different numbers of electrons E) atoms in the same horizontal period The element _______________ is classified as a metal whereas ______________ is classified as a nonmetal. A) Ca, N B) P, Zn C) Se, F D) Fe, Cd E) Ge, Cl In an atom of A) B) C) D) E) 34 16 7. 8. S __________. the number of protons equals the number of neutrons 18 electrons are found outside the nucleus 16 neutrons are found in the nucleus the sum of protons and neutrons is 34 the total number of electrons and protons equals 34 EXAM 1 VERSION A Page 4 of 9 Chem 142 VERSION A Summer 2011 MULTIPLE CHOICE: SHORT CALCULATIONS. 8 @ 5 pts each 40 TOTAL POINTS Please mark the one correct answer for each of the following questions on your scantron. 9. The density of magnesium metal (used in fireworks) is 1.65 kg/m3. Express this density in g/cm3. A) 1.65 x 10-3 g/cm3 B) 1.65 x 10-1 g/cm3 C) 1.65 x 101 g/cm3 D) 1.65 x 103 g/cm3 E) none of the above 10. Hydroquinone, used as a photographic developer, is 65.4% C, 5.5% H, and 29.1% O, by mass. What is the molecular formula of hydroquinone if the molecular mass is 110.1 amu? A) C5H18O2 B) C6H6O2 C) C4H14O3 D) C3H3O E) none of the above 11. Calculate the moles of sodium ions present in a milliliter of 0.235 M sodium bicarbonate. A) 2.35 x 10-1 moles B) 4.70 x 10-1 moles C) 2.35 x 10-4 moles D) 4.70 x 10-4 moles E) none of the above 12. What volume of 2.050 M copper(II) sulfate must be diluted with water to prepare 750.0 mL of a 0.8612 M sulfate solution? A) 892.6 mL B) 315.1 mL C) 1.785 mL D) 157.5 mL E) none of the above EXAM 1 VERSION A Page 5 of 9 Chem 142 VERSION A Summer 2011 13. An ionic compound forms when lithium reacts with oxygen. If a sample of the compound contains 5.3 x 1020 lithium ions, how many moles of oxide ions does it contain? A) 4.4 x 10-4 mol B) 1.6 x 1044 mol C) 1.8 x 10-3 mol D) 8.8 x 10-4 mol E) none of the above 14. What is the mass % of H in ammonium phosphate ((NH4)3PO3? A) 2.3% B) 6.0% C) 9.1% D) 17% E) none of the above 15. Naturally occurring rubidium has an atomic mass of 85.5amu. It is composed of two isotopes, rubidium85 (84.9amu) and rubidium87 (86.9amu). From this information one can conclude that naturally occurring rubidium is composed of ______________. A) approximately 30% rubidium-85 and 70% rubidium-87 B) approximately 70% rubidium-85 and 30% rubidium-87 C) approximately 20% rubidium-85 and 80% rubidium-87 D) approximately 80% rubidium-85 and 20% rubidium-87 E) none of the above 16. What is the correct name of Sn(HSO4)2? A) tin(IV) sulfite B) tin(II) sulfate C) tin(IV) sulfate D) tin(II) hydrogen sulfate E) tin(IV) hydrogen sulfate EXAM 1 VERSION A Page 6 of 9 Chem 142 VERSION A Summer 2011 MATCHING. 8 @ 2 pts each 16 POINTS TOTAL Please indicate the letter of the one correct answer for each of the following questions in the blank. 17. The conversion of CO2 (g) into CO2 (s) is an example of a _____ change/reaction. 18. Give the chemical symbol/name (whichever is missing) for each of the following elements: A) Oxygen _______ B) Bromine _______ C) Ca _______ D) Potassium _______ E) Iodine _______ 19. According to the Law of ________________ a pure compound always contains the same elements in exactly the same proportions by mass. 20. The atomic number of an element is equal to its number of ___________. A) E) I) M) Q) U) X) Physical B) Calcium F) Protons J) Sodium N) Nickel R) Neutrons V) Multiple Proportions K C) Chemical D) Os Electrons G) Nitrogen H) I B K) Decomposition L) Fe Ir O) Sulfur P) In P S) Carbon T) O Lead W) Br Y) Definite Proportions Z) Conservation of Mass EXAM 1 VERSION A Page 7 of 9 Chem 142 VERSION A Summer 2011 LONG ANSWER. 20 POINTS TOTAL 21. In lab, a student mixes 4.0 mL of 3.0 M lead(II) nitrate reacts with 9.0 mL of 2.5 M sodium chloride in aqueous solution to form a precipitate. A) What is the net ionic equation for this reaction? (3 pts) Please use your answer from part A for the calculations in parts B-D. If you are unable to write the balanced net ionic equation or no precipitate would form in this reaction (i.e., no reaction would occur), use the following information for the remainder of the problem: 60. mL of 0.50 M iron(III) chloride solution and 40.0 mL of 7.5 M ammonium sulfide solution are mixed in order to precipitate iron(III) sulfide according to the following balanced net ionic equation: 2Fe3+ (aq) + 3S2- (aq) Fe2S3 (s) B) Assuming the reaction goes to completion, what mass of precipitate will form? (6 pts) EXAM 1 VERSION A Page 8 of 9 Chem 142 VERSION A Summer 2011 C) What mass of each excess ion will remain? (9 pts) D) If the student recovers 2.00 g of precipitate, what is the percent yield? (If you did not calculate a theoretical yield in part B, use 3.53 g here) (2 pts) EXAM 1 VERSION A Page 9 of 9 ...
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This note was uploaded on 01/19/2012 for the course CHEM 142A taught by Professor Campbell during the Summer '11 term at University of Washington.

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