Chp 13, 14, 15 SHOW ALL WORK AND CIRCLE FINAL ANSWERS. a) 1 only b) 2 only c) 3 only d) 1 and 2 only e) 1, 2, and H 2

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1 Chp 13, 14, 15 Name: SHOW ALL WORK AND CIRCLE FINAL ANSWERS 1. Which of the following factors affect the initial rate of a reaction? 1) The nature of the reactants. 2) The concentration of the reactants. 3) The size of solid reactant particles. a) 1 only b) 2 only c) 3 only d) 1 and 2 only e) 1, 2, and 3 2. For the reaction IO 3 + 5I + 6H + 3 I H 2 O the rate of disappearance of I at a particular time and concentration is 5.0 x 10 3 M s 1. How is the rate of reaction of I related to the rate of reaction of H + What is the rate of disappearance of H + in M s 1? 3. The rate law for the oxidation of the iodide ion by the chlorate ion in aqueous acidic solution, ClO I + 6 H+ 3 I 3 + Cl + 3 H 2 O has been found to be Rate = k [ClO 3 ] [I ] [H + ] 2 a) the overall order for the reaction is b) What are the units of k when time is in seconds and the concentration is in moles per liter? 4. Which of the following statements is always true? a) Exothermic reactions have lower activation energies than endothermic reactions. b) The rate for a reaction depends on the concentrations of all the reactants. c) The rate of a catalyzed reaction is dependent on the concentration of the catalyst. d) The specific rate constant is dependent on the concentrations of the reacting species. e) The rate law can be determined from the stoichiometric equation. 5. The reaction of iodide ion with hypochlorite ion, OCl (which is found in liquid bleach), follows the reaction OCl + I OI + Cl It is a rapid reaction that gives the following rate data. a) What is the rate law for the reaction? Experiment number [OCl ] [I ] Initial rate M/s x x x x x x x x x 10 4 b) What is the numerical value of k?

2 6. Explain how a catalyst speeds up a chemical reaction. (Write in complete sentences.) 7. The thermal decomposition of phosphine (PH 3 ) into phosphorus and molecular hydrogen is a first-order reaction: 4 PH 3 P H 2 The half-life of the reaction is 35.0 s at 680 o C. a) Calculate the first-order rate constant for the reaction. b) the time required for 95 percent for the phosphine to decompose. 8. The reaction CHCl 3 + Cl 2 CCl 4 + HCl has been proposed to occur by the mechanism Cl 2 2 Cl fast equilibrium CHCl 3 + Cl HCl + CCl 3 slow step CCl 3 + Cl CCl 4 very fast equilibrium Predict the overall experimental rate law for this mechanism. 9. Assuming that the system is at equilibrium a) Which of the following reactions goes essentially to completion and explain your reasoning. b) Which of the following reactions does not take place to a significant extent? i) Br 2 + Cl 2 2 BrCl K c = 7.0 ii) C (graphite) + O 2 CO 2 K c = 1.3 x iii) 2 CH 4 HC CH + 3 H 2 K c = iv) Br 2 2 Br K c = 4 x 10 v) 2 HF H 2 + F 2 K c = 1.0 x 10 95

3 10. Explain why either partial pressures or concentrations can be used to write equilibrium constant expressions for gaseous reactions. 11. If K c = 2.5 x 10 2 for the equilibrium 2 H 2 + S 2 2 H 2 S when a mixture with [H 2 ] = 7.6 x 10 4 M, [S 2 ] = 6.8 x 10 5 M and [H 2 S] = 3.2 x 10 5 M reaches equilibrium, which concentrations will have increased and which concentrations will have decreased. Explain your answer. 12. The value of K c for the equilibrium N 2 2 NO 2 is 4.64 x 10 3 and the equilibrium concentration of NO 2 formed by the decomposition of pure N 2 is 1.54 x 10 2 M. a) What is the equilibrium concentration of N 2? 13. Write the equation for the equilibrium that corresponds to the following equilibrium constant expression. K c = [NO]4 [H 2 O] 6 [NH 3 ] 4 [O 2 ] The reaction of carbon monoxide and diiodine pentoxide as represented by the equation 5 CO + I 2 O 5 I CO 2 is endothermic. the yield could be increased by a) increasing the pressure. b) decreasing the pressure. c) increasing the temperature. d) decreasing the temperature. e) decreasing the volume of the reaction vessel.

4 15. Consider the equilibrium PCl 3 + Cl 2 PCl 5 H = 92 kj Give at least three suggestions of ways to increase the concentration of PCl 3 at equilibrium. 16. In an analysis of interhalogen reactivity, mol ICl was placed in a 5.00 L flask and allowed to decompose at high temperature: 2 ICl I 2 + Cl 2 Calculate the equilibrium concentrations of I 2, Cl 2 and ICl. K c = at this temperature. 17. A) Which of the following is a weak base in aqueous solution? a) N 2 H 4 b) HOCl c) LiOH d) NaOH e) Ca(OH) 2 B) Which of the following is a strong acid in water? a) HF b) HI c) H 3 d) H 2 CO 3 e) HClO For the Brønsted-Lowry acid-base reaction S 2 (aq) + H3 O + (aq ) HS (aq) + H2 O (l) a) Classify each of the species as an acid or a base. b) Decide which species (reactants or products) are favored at the completion of the reaction. 19. Which of the following species are amphiprotic a) H 3 b) H 2 c) H 2 d) All of the following would be expected to be able to function as Lewis bases except a) O 2 b) OH c) N 3 d) NH 3 e) NH 4 +

5 21. Which of the following is a strong acid in water (relative to the other acids present)? a) (HO) 2 SO b) (HO)ClO c) (HO) 2 CO d) (HO) 3 PO e) (HO) 2 SO A solution has a hydrogen-ion concentration of M. what is the ph of the solution? 23. Arrange the following compounds in order of increasing acid strength. HCl, H 2 O, H 2 S 24. An antiseptic solution at 25 o C has a hydroxide-ion concentration of 8.4 x 10 5 M. Is the solution acidic, neutral or basic. (show your work) 25. A 1.00 L aqueous solution contained 6.78 g of barium hydroxide, Ba(OH) 2. What was the ph of the solution at 25 o C?