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Unformatted text preview: One point is earned for a correct identification of a precipitate that would form upon the mixing of the chosen solutions. Mix an aqueous solution of BaCl2. 2H2O with an aqueous solution of CuSO . 5H O.
4 2 The BaSO4 will precipitate. © 2008 The College Board. All rights reserved. Visit the College Board on the Web: www.collegeboard.com. AP® CHEMISTRY 2008 SCORING GUIDELINES (Form B)
Use principles of thermodynamics to answer the following questions. (a) The gas N2O4 decomposes to form the gas NO2 according to the equation below. (i) Predict the sign of ΔH° for the reaction. Justify your answer. Bonds are broken when NO2 molecules form from N2O4 molecules. Energy must be absorbed to break bonds, so the reaction is endothermic and the sign of ΔH° is positive. One point is earned for the correct sign and a correct explanation. (ii) Predict the sign of ΔS° for the reaction. Justify your answer. There are two gaseous product molecules for each gaseous reactant molecule, so the product has more entropy than the reactant. The entropy increases as the reaction proceeds, so the sig...
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This note was uploaded on 05/05/2011 for the course CHEM 504 taught by Professor John during the Fall '11 term at American College of Computer & Information Sciences.
- Fall '11