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Unformatted text preview: Chemistry 20L Winter 2008 Midterm Exam #1 NAME: ____________________________________________________________________ (LAST NAME) (FIRST NAME) ID #: _____________________ Section (circle) 1A (T 8-11, James) 1F (Th 11-2, James) 1B (T 2-5, Kevin) 1G (Th 11-2, Kristina) 1C (T 6:30-9:20, Kevin) 1H (Th 2-5, Eunshil) 1D (W, 2-5, Kristina) 1I (Th 6:30-9:20, Mikhail) 1E (Th 8-11, Eunshil) 1J (F 2-5, Mikhail) DO NOT OPEN THE EXAM UNTIL YOU ARE INSTRUCTED TO DO SO. READ THE FOLLOWING INSTRUCTIONS CAREFULLY. INSTRUCTIONS 1. This is a closed book and closed note exam. You may use your 4 x 6 note card during the exam. An equation sheet is provided at the end of the exam. 2. Calculators are allowed. 3. Use PEN to answer ALL questions. You will not be allowed a regrade if you use pencil for ANY part of the exam. 4. There are a total of 6 pages of questions. 5. Show all work for all calculations in order to receive full credit. No credit will be given for a numerical answer alone or for an illegible answer. 7. You must provide correct units and significant figures . 8. Place a box or circle around your final calculated answer. Page Value Max. Score 2 8 3 12 4 8 5 10 6 12 Total 50 I. Definitions Name a 2 (A) (4 points) Briefly define the following terms in no more than 2-3 sentences. 1. Accuracy ANSWER: Defines the closeness of a result to the true value. 2. Precision ANSWER: Defines the closeness of a set of results to each other, the reproducibility of a result, or the number significant figures in a result. II. Basic Calculations One of the active ingredients in Colgate liquid toothpaste gel is sodium fluoride (NaF). Sodium fluoride is used as an anticavity agent. In the liquid gel form, the concentration of sodium fluoride is approximately 0.240 % ( w/v% ). (A) (4 points) If the total volume of a container of Colgate liquid gel is 136 mL, calculate the concentration of sodium fluoride in ppm ....
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- Winter '08