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Unformatted text preview: apstudents (for students and parents). AP® CHEMISTRY
2007 SCORING GUIDELINES (Form B)
Question 4
For each of the following three reactions, in part (i) write a balanced equation for the reaction and in part (ii)
answer the question about the reaction. In part (i), coefficients should be in terms of lowest whole numbers.
Assume that solutions are aqueous unless otherwise indicated. Represent substances in solutions as ions if the
substances are extensively ionized. Omit formulas for any ions or molecules that are unchanged by the reaction.
You may use the empty space at the bottom of the next page for scratch work, but only equations that are
written in the answer boxes provided will be graded.
(a) Solid ammonium carbonate decomposes as it is heated.
(i) Balanced equation:
(NH4)2CO3 → 2 NH3 + CO2 + H2O One point is earned for the correct reactant.
Two points are earned for correct products.
One point is earned for balancing mass and charge. (ii) Predict the algebraic sign of ΔS ° for the r...
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 Spring '09
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