Final Problems

# Final Problems - Review session Problem 1 You decide to be...

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Review session May 06, 2008 Problem 1. You decide to be constructive during the summer break. You help your mother clean the house and do groceries. Since she sees you are doing so much work, she thinks you need to get more energy. So every afternoon she makes hot chocolate for you. However, she always makes the cocoa way too hot and the marshmallows dissolve. You promised yourself you will not have a fight with your mom on silly things, so you put some marshmallows in the freezer (0 o C ). Now the marshmallows don't dissolve quickly in the mouthwatering brown liquid! You have two large marshmallows that weigh 2.2 grams all together. The specific heat of the marshmallows is 1.34 J/g o C. You place the two marshmallows in a 175 mL scalding liquid, which has an initial temperature of 82 o C (holy smokes!!!). What will be the final temperature of the hot chocolate and will it be cool enough to drink? (for hot chocolate specific heat = 4.2 J/g K, density = 1.0 g/mL). Problem 2. Find the Δ H o f for CH 4 (g) with the given information. (1) C(s) + O 2 (g) CO 2 (g) Δ H o 1 = -393.5 kJ mol -1 (2) H 2 (g) + ½ O 2 (g) H 2 O (l) Δ H o 2 = -285.8 kJ mol -1 (3) CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2H 2 O (l) Δ H o 3 = -890.3 kJ mol -1 Problem 3. Ethyl acetate (CH 3 CO 2 CH 2 CH 3 ) reacts with sodium hydroxide in aqueous solution to form the salt sodium acetate and ethanol. The initial rate of this so-called saponification is determined under several conditions Expt Rate (M min -1 ) [ester] M [NaOH] M [Ethanol] 1 1.77 * 10-5 0.012 0.012 0 2 2.95* 10-4 0.20 0.012 0 3 3.69 * 10-4 0.03 0.10 0 4 1.48 * 10-4 0.012 0.10 0.10 CH 3 CO 2 CH 2 CH 3 + NaOH CH 3 CO 2 Na + HOCH 2 CH 3 a. What is the kinetic order of this reaction in ester concentration.

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