This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Chem 1B Exam 1 Sample Questions Instructions: For all mathematical problems, show your work. Give the basic formula (if there is one), rearrange it if necessary, plug in data with units, round properly to the correct number of significant figures, and place a box around the answer. For essay questions, be complete, but concise. Complete sentences with proper spelling and punctuation are expected. Useful information: R = 8.314 J/mol . K ln[X] t = -kt + ln[X] o 1 [X] t = kt + 1 [X] o [X] t = -kt + [X] o R = 0.08206 L . atm/mol . K ln(k) = - E a R 1 T + ln(A) ln k 1 k 2 = E a R 1 T 2- 1 T 1 For questions 1-6, choose the one best answer for each. 1. (2 pts.) Which of the following statements is true? (a) Endothermic reactions have higher activation energies than exothermic reactions. (b) The rate law for a reaction depends on the concentrations of all reactants that appear in the stoichiometric equation. (c) Reaction rates are related to ∆ E values for reactions. (d) A catalyst increases a reaction rate by providing more energy to the reactants. (e) The rate constant for a reaction is independent of the concentrations of the reacting species. 2. (2 pts.) Consider the freezing of liquid water at -10°C. For this process what are the signs of ∆ H , ∆ S, and ∆ G? ∆ H ∆ S ∆ G (a) + + + (b) - - - (c) + - - (d) - + + (e) - - + 3. (2 pts.) Consider the dissociation of hydrogen: H 2 (g) → 2H(g) One would expect that this reaction (a) will not be spontaneous at any temperature. (b) will be spontaneous at any temperature. (c) will be spontaneous at high temperature. (d) will be spontaneous at low temperature. (e) will never happen. 4. (2 pts.) The third law of thermodynamics states (a) the entropy of the universe is constant. (b) the entropy of the universe is increasing. (c) the absolute entropy of a substance decreases with increasing temperature. (d) the entropy of the universe equals the sum of the entropy of the system and the entropy of the surroundings....
View Full Document
This note was uploaded on 12/21/2010 for the course CHEM 1B taught by Professor Garyj.decicco during the Fall '10 term at Santa Rosa.
- Fall '10