Chemistry 116: Exam 3 March 25, 2014

Transcription

1 March 5, Each of the following pairs contains one strong acid and one weak acid except a. HNO3 and HCO3 b. HF and HNO c. HSO4 and HS d. HCH3O and HCl e. HBr and H3PO4. Given that KB of CH3NH is at 5 o C, what is the equilibrium constant for the reaction a b c d e CH3NH3 + + HO(l) CH3NH(aq) + H3O + (aq) 3. Given the net ionic equation HO(l) + CO3 (aq) HCO3 (aq) + OH (aq) a. HO is an acid and OH is its conjugate acid b. HO is an acid and OH is its conjugate base c. CO3 is a Bronsted-Lowry acid because it is a proton acceptor d. HO is a Lewis acid because it is a proton donor e. HO is a Lewis base because it is an electron pair donor 4. The reaction of carbon monoxide and diiodine pentoxide is endothermic. The yield could be increased by 5 CO(g) + IO5(g) I(g) + 5 CO(g) a. Increasing the pressure by decreasing volume b. Decreasing the temperature c. Increasing the temperature d. Both a and b e. Both a and c 5. The ionization constant of water at 60 o C is What is the ph of pure water at this temperature? a b c d e Page 1 of 5

2 March 5, Consider the reaction of the shown below at a given temperature. When the system is at equilibrium, the molar concentrations of Br, Cl, and BrCl are M, M, and M, respectively. What is the value of Kc for this system? a. 0.5 b. 3.9 c. 7 d. 53 e. 60. Br(g) + Cl(g) BrCl(g) 7. The reaction mixture of CO and O at a given temperature is given below. When equilibrium is established, which of the following ratios is constant regardless of the initial concentrations of CO and O? CO(g) + O(g) CO (g) a. [ O b. [ O c. [ O d. [ O e. 1 [ O 8. Consider the reaction shown below. At a certain temperature Kc equals What will happen if mole of HS, 1.0 mole of H, and 1.5 mole of S(g) are added to a.0 L container HS(g) H(g) + S(g) a. Nothing, the system is at equilibrium b. More HS will be formed c. H will be formed 9. At a given temperature, mole NO, mole Cl and 0.50 mole of ClNO were placed in a 10.0 liter container and allowed to come to equilibrium. At equilibrium moles of ClNO are present. What is the value of the equilibrium constant, Kc? a b c d e ClNO(g) NO(g) + Cl(g) Page of 5

3 March 5, The KB of piperidine (an organic base) is What is the ph of a M solution of piperidine? [Be careful a..67 b..80 c d e Calculate the ph of a 0.017M solution of Ba(OH) a b c d e Which of the following mixtures is suitable for making buffers? I. CH3COOH and NaCH3COO II. HF and NaF III. NH4Cl and NH3 d. I and III only e. I, II, and III 13. Carbon disulfide and chlorine react according to the equation given below. When 1.00 mole of CS and 3.00 mole of Cl are placed in a.00 liter container and allowed to come to equilibrium, the mixture is found to contain 0.50 mole of CCl4. What is the amount of Cl at equilibrium? a..5 mole b..75 mole c mole d. 0.5 mole e mole CS(g) + 3 Cl(g) SCl(g) + CCl4(g) Page 3 of 5

4 March 5, A state of dynamic equilibrium exists at constant temperature for I. A stoppered flask half full of water II. An open pan of boiling water III. A stoppered flask of saturated sodium carbonate solution d. I and II only e. I and III only 15. For the reaction NO(g) + ½ O(g) NO(g) at 750 o C, the equilibrium constant Kc equals a. Kp (RT) 3/ b. Kp (RT) 3/ c. Kp (RT) /3 d. Kp (RT) 1/ e. Kp (RT) 1/ 16. What is the ph of a 0.5M solution of hypobromous acid (HOBr, KA= ) a b c. 3.5 d e All of the following are acid-base conjugate pairs except a. CH3NH, CH3NH3 + b. HCO3, HCO3 c. HNO, NO + d. HOCl, OCl e. HSO4, HSO4 18. A 0.10 M aqueous solution of an acid HA has a ph of What is the value of KA for this acid? a b c d e Page 4 of 5

5 March 5, The equilibrium constant, KC, for the reaction below is 7.4 at 45 o C. The numerical value of value of the equilibrium constant will be changed if ½ H(g) + ½ I(g) HI(g) KC= 7.4 I. The volume of the container is changed II. The temperature is doubled to 500 o C III. The amounts of reactants are doubled d. I and II only e. II and III only 0. For which of the following is the reaction yield the smallest when equilibrium is reached. a. Kc = b. Kc = c. Kc = d. Kc = e. Kc = Bonus: What is the net ionic reaction that occurs when hydrochloric acid is added to the NaHCOO/ HCOOH buffer? a. H + (aq) + HO(l) H3O + (aq) b. H + (aq) + OH (aq) HO(l) c. H + (aq) + HCOO (aq) HCOOH(aq) d. HCl(aq) OH (aq) HO(l) + Cl (aq) e. HCOOH H + (aq) + HCOO (aq) Key 1. B. A 3. B 4. C 5. B 6. B 7. D 8. B 9. D 10. D 11. E 1. E 13. A 14. E 15. D 16. D 17. C 18. B 19. B 0. D 1. C Page 5 of 5