Chemistry 112 Name Homework Exam I Form A Section May 25,

Transcription

1 Chemistry 11 Name Homework Exam I Form A Section May 5, 01 IMPORTANT: On the scantron (answer sheet, you MUST clearly fill your name, your student number, section number, and test form (white cover = test form A; yellow cover = test form B. Use a # pencil. There are 5 questions on this exam. Check that you have done all of the problems and filled in the first 5 bubbles on the scantron. The maximum score on this exam is 5 points. Your score will be reported in percent (max 100%. Exam policy Hints Calculators with text-programmable memory are not allowed. Relevant data and formulas, including the periodic table, are attached at the end of this exam. Your grade will be based only on what is on the scantron form. The answer key will be posted on the web after the exam (on the Exam Schedule page. You must turn in your cover sheet with your scantron answer form. As you read the question, underline or circle key words to highlight them for yourself. Avoid errors from "mis-reading" the question. Pay attention to units and magnitudes (decimal places of numbers obtained from calculations. There is no penalty for guessing.

2

3 CHEMISTRY 11 Homework Test 1 May 5, 01 FORM A 1. For the endothermic reaction 4 NO (g + O (g N O 5 (g the activation energy is 1 kj/mol and the overall E is + kj/mol. What is the activation energy of the reverse reaction? A. 100 kj/mol B. 146 kj/mol C. 146 kj/mol D. 100 kj/mol E. can t be determined from the information given. Which type of radioactive decay converts a neutron to a proton? A. decay B. emission C e emission only D. 0-1e capture only E. either + 1e emission or - 1e capture. What is the poh of a M solution of HCl? A..4 B C. 5.4 D. 8.6 E. HCl is a strong acid. The poh cannot be calculated.

4 4. The missing product in this reaction combines with oxygen to form a compound with the formula. A. M O B. MO C. MO D. M O 4K e +??? E. The product is an inert gas. It won t react with oxygen. 5. All of the following are conjugate acid-base pairs, except: A. H O +, OH B. 4 +, C. HCO, CO D. HC H O, C H O E. HCl, Cl 6. The data in the table below were obtained for the reaction: BF (g + (g F B (g Experiment [BF ] M [ ] M Initial Rate (M/s What is the value of the rate constant k? A..408 M 1 s 1 B s 1 C. 1.6 s 1 D M 1 s 1 E M 1 s 1

5 7. In a graph of experimental data to determine the activation energy, A. the overall rate is plotted against the absolute temperature. B. the rate constant is plotted against the inverse of the absolute temperature. C. the natural logarithm of the rate constant is plotted against the absolute temperature. D. the natural logarithm of the rate constant is plotted against the inverse of the absolute temperature. E. the inverse of the rate constant is plotted against the absolute temperature. 8. The decomposition of hydrogen peroxide via the following mechanism was demonstrated in class. H O (aq + I (aq IO (aq + H O (aq H O( + IO (aq H O( + O (g + I (aq If the first step is the rate determining step, what is the rate law for this reaction? A. Rate = [H O ] [I ] B. Rate = [H O ] C. Rate = [H O ] [I ] D. Rate = [H O ][IO ] E. Rate = [H O ] [IO ] 9. The combustion of ethylene proceeds by the reaction: C H 4 (g + O (g CO (g + H O(g When the rate of disappearance of O (g is M s 1, what is the rate of appearance of H O (g? A M s 1 B M s 1 C M s 1 D M s 1 E M s 1

6 10. One possible mechanism for an enzyme catalyzed reaction is given below where E = enzyme, S = substrate and P = product E + S ES (fast ES E + P (slow What is the experimentally measured rate law that is consistent with this mechanism? A. rate = k [ES] B. rate = k [E] C. rate = k [E] [S] D. rate = k [E] ½ E. rate = k [E] [S] ½ 11. If enough of each of the following compounds were dissolved in water to give a 1.00 M solution of each, which would have the highest ph? A. HCl B. NaCl C. NaC H O D. NaI E. 4 Cl 1. The ph of 0.10 M HA solution is What is the value of K a for HA? A B C D E Go on to the next page

7 A compound HX(aq is a weak acid. Which of the following is correct? A. X (aq is also a weak acid. B. X (aq is a weak base. C. X (aq is a strong base. D. X (aq is a strong acid. E. X (aq has negligible strength as either an acid or a base. 14. Which of the following is the weakest acid? A. HBr B. HClO 4 C. H SO 4 D. H PO 4 E. HPO Which of the following is the strongest Lewis base? A. Cs + B. F C. Ba + D. Fe + E. H O I has a half-life of 8.04 days. Assuming you start with a 1.5 mg sample of 11 I, how many mg will remain after 1.0 days? A mg B mg C. 0.4 mg D mg E mg Go on to the next page

8 17. Which of the following is the strongest acid? 18 What is the ph of a solution made by mixing 00mL of M NaOH with 50.0 ml M KOH and 5.0 ml of M RbOH(aq? A. 11. B..75 C D. 1. E Go on to the next page

9 1 / [A] 19. Citric acid, which we denote as H A, is a triprotic acid with K a1 = , K a = and K a = What is the ph of a solution prepared by dissolving moles of Na A (the sodium salt of A in 1 liter of water? A. 4.0 B C D E Acrylic acid, which is used to make many different types of plastics and other commercial polymers, has a pk a value of 4.5 at 5 C. Calculate the value of the base dissociation constant (K b at 5 C for acrylate, the conjugate base of acrylic acid. A B C D E The rate of a reaction was measured and the following data was obtained. The slope is 0.1 M 1 s 1 and the y-intercept for this plot is.85 M 1. How long will it take for the reactant concentration to decrease to 0.1 M? A s B. 0.50s C. 1.0 s D. 0 s E. 44 s time (s Go on to the next page

10 . What is the equilibrium constant expression for the hydrolysis of dimethylamine, (CH? A. K b OH B. C. K b K b H OH D. E. H N K b CH OH K b CH. The mass of the nucleus of an 56 Fe atom is amu. What is the nuclear binding energy for 56 Fe? A J B J C J D J E J Go on to the next page

11 4. 40 K is a weak emitter with a half-life of s. The activity of a sample of KNO is disintegrations per second. Assuming that 40 K is the only source of decay, how many atoms of 40 K are in the sample? A atoms B atoms C atoms D atoms E atoms 5. A particular first-order reaction has a rate constant of s 1 at 5 C. What is the magnitude of k at 75 C if E a = 85.8kJ/mol? A s 1 B s 1 C. 670 s 1 D s 1 E s END OF HOMEWORK EXAM 1