Chemistry > EXAM > Prelim 2 2015 | Download for quality grades (All)

Prelim 2 2015 | Download for quality grades

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There are 7 (mostly multipart) questions and a total of 15 pages (including this cover sheet, a blank page after all the questions, a page of potentially useful facts and a periodic table at the end). Make sure that your examination booklet is complete. The prelim is not designed with the idea that all, or necessarily any of you, will complete each and every question. Write your answers directly on these sheets. Use the blank page, or if necessary the backs of pages, but clearly indicate on the problem page where work can be found. Additional pages should be securely attached to the rest of the test book. Be brief, concise, and neat. Proctors are not allowed to interpret questions for you. In case of doubt, indicate the assumptions on which your answer is based. No additional formulas, or values of fundamental constants, are required to answer these questions; if you believe that there is missing information, please check to make sure that you have taken advantage of any information provided to you in the problem, or on the page of useful information. You may leave when you are finished, except in the final minutes of the exam. Question 1. (14) Question 2. (12) Question 3. (16) Question 4. (12) Question 5. (12) Question 6. (18) Question 7. (16) Total (100) Show your work! (Unless you don’t care to receive partial credit). Many of the questions in this exam might seem to be answerable with just a “lucky guess”; full credit will require some explanation for your guess. 1 1. (14 points) (a) Write the balanced net ionic equation (i.e. eliminate all spectator ions) for the reaction below which takes place in acidic solution. I − (aq) + IO− 3 (aq) → I − 3 (aq) (b) Write the balanced net ionic equation (i.e. eliminate all spectator ions) for the reaction below which takes place in basic solution. S2O 2− 4 (aq) + CrO2− 4 (aq) → Cr(OH)3 (s) + SO2− 3 (aq) as done in class 2 (c) For four unknown elements (call them A, B, C and D) it is found that A + B + → A + + B B + D+ → B+ + D C + + D → No Reaction B + C + → B+ + C Which of the four atoms is the strongest reducing agent, and which is the weakest reducing agent? Strongest: Weakest: 2. (12 points) (a) A student is told to draw a Lewis structure and VSEPR structure for a molecule with empirical formula ClO3. What do you think she drew? Assume that the molecular formula was, in fact, ClO3. Make sure to include multiple bonds/lone pair electrons as required to complete the structure. 3

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