CH3NH2(aq) + H3O + (aq) 3. The reaction of carbon monoxide and diiodine pentoxide is endothermic. The yield could be increased by

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1 1. What is the ph of a M HClO4 solution? a b c d Chemistry 116: Exam 2 2. Given that KB of CH3NH2 is at 25 o C, what is the equilibrium constant for the reaction below? a b c d e CH3NH3 + + H2O(l) CH3NH2(aq) + H3O + (aq) 3. The reaction of carbon monoxide and diiodine pentoxide is endothermic. The yield could be increased by 5 CO(g) + I2O5(g) I2(g) + 5 CO2(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 4. What is the ph of a 0.25M solution of hypobromous acid (HOBr, KA= ) a b c d e If the KA of an acid is , what is the pkb for its conjugate base? a b c d e It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 1 of 6

2 6. If solid NaNO2 was added to a solution of HNO2 at equilibrium. Hint: Write the equilibrium reaction of HNO2 and water. a. The ph of solution would decrease b. [H + ]=[NO2 ] c. The amount of HNO2 in solution would increase d. The ph of the solution would remain the same e. A precipitate would form 7. Phosphoric acid is a triprotic acid, ionizing in the following sequential steps: H3PO4(aq) + H2O(l) H2PO4 (aq) + H3O + 3 (aq) K = 7.2 A1 10 H2PO4 (aq) + H2O(l) HPO4 2 (aq) + H3O + 8 (aq) K = 6.3 A2 10 HPO4 2 (aq) + H2O(l) PO4 3 (aq) + H3O + 13 (aq) K A2 = Which equilibrium is most important in determining the ph of a solution of phosphoric acid? a. H2PO4 (aq) + H2O(l) HPO4 2 (aq) + H3O + (aq) b. HPO4 2 (aq) + H2O(l) PO4 3 (aq) + H3O + (aq) c. H3PO4(aq) + H2O(l) H2PO4 (aq) + H3O + (aq) 8. What is the net ionic reaction that occurs when hydrochloric acid is added to the HCOONa/ HCOOH buffer? a. H3O + (aq) + OH (aq) H2O(l) b. HCl(aq) + OH (aq) H2O(l) + Cl (aq) c. HCOOH H + (aq) + HCOO (aq) d. H3O + (aq) + HCOOH(l) H3O + (aq)+ CH3COO (aq) e. H3O + (aq) + HCOO (aq) HCOOH(aq) + H2O(l) 9. Identify the base in the following reaction: NH2 (aq) + H20(l) NH3(aq) + HO (aq) a. H20(l) b. NH3(aq) c. HO (aq) d. NH2 (aq) 10. Determine [H3O + ] when ph = a mole/l b mole/l c mole/l d mole/l e mole/l It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 2 of 6

3 11. A particular drain cleaner contains NaOH. What is the ph of a solution produced when 5.0 g of NaOH (40.00 g/mole) dissolves in enough water to make 350 ml of solution? a b c d e Determine [H3O + ] for a solution of aqueous ammonia where [OH ] is M a mole/l b mole/l c mole/l d mole/l e mole/l 13. A newspaper reported that the level of acidity in a sample taken from an extensively studied watershed in New Hampshire in February 1998 was an astounding 210 times lower than the worst measurement taken in the preceding two decades. What is this difference expressed in units of ph? a. 3.3 b. 14 c. 5.3 d. 210 e On the basis of the following degree-of-ionization data for M solutions, select which acid has the smallest KA. Acid Degree of Ionization (%) a HF 8.5 b HN3 1.4 c CH3COOH 1.3 d C6H5COOH Calculate the concentration of C3H7COO for the dissociation of butanoic acid if a M solution of butanoic acid (C3H7COOH) is 1.23% ionized. a M b M c M d M It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 3 of 6

4 16. Calculate the ph of a M solution of HNO2. a b c d. No way to determine, need KA value of HNO2 e What is the role of (CH3)3NH + (aq) in the reaction below (CH3)3N(aq) + H2O(l) (CH3)3NH + (aq) + HO (aq) a. It is acting as a base b. No way to determine c. It is the conjugate acid of (CH3)3N(aq) d. It is the conjugate base of (CH3)3N(aq) e. It is acting as an acid 18. An acetic acid buffer containing 0.50 M CH3COOH and 0.50 M CH3COONa has a ph of 4.74 What will the ph be after mol of HCl has been added to 1.00 liter of the buffer? a b c d e Dimethylamine, (CH3)2NH is a weak base with KB at 25 C. Calculate the ph of a 0.90M solution of dimethylamine. a b c d e It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 4 of 6

5 20. Phosphate buffers are commonly used in biological research. If a small amount of strong acid is added to a buffer solution that is M H3PO4 and M KH2PO4, which of the following statements is true? a. [H3PO4] will increase, [KH2PO4] will decrease, and ph will not change. b. [H3PO4] will increase, [KH2PO4] will decrease, and ph will slightly increase. c. [H3PO4] will increase, [KH2PO4] will decrease, and ph will slightly decrease. d. [H3PO4] will decrease, [KH2PO4] will increase, and ph will slightly decrease. e. [H3PO4] will decrease, [KH2PO4] will increase, and ph will slightly increase. 21. Solutions of are basic. a. NaF b. NaCl c. NaBr d. NaI e. Both a and d 22. What is the [H3O + ] in a balanced buffer solution of HCNO (KA= ) and NaCNO? a M b M c M d M e M 23. Three buffers are as shown below. Rank the three buffers from lowest ph to highest ph. Buffer 1 equal concentrations of formic acid (HCOOH, KA= ) and sodium formate, 2 equal concentrations of hydrofluoric acid (HF, KA= ) and sodium fluoride 3 equal concentrations of acetic acid (CH3COOH, KA= ) and sodium acetate a. Buffer 2 < Buffer 1 < Buffer 3 b. Buffer 3 < Buffer 2 < Buffer 1 c. Buffer 2 < Buffer 3 < Buffer 1 d. Buffer 1 < Buffer 2 < Buffer 3 e. Buffer 3 < Buffer 1 < Buffer 2 It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 5 of 6

6 24. When mixed with equal volumes, which of the following solutions would function as an effective ph buffer? a M NaClO and M HClO b M HNO3 and M NaNO3 c M NaCl and M HCl d M HNO2 and M NaNO3 e M NaOH and M HCl 25. A solution is prepared by adding 0.10 mole of potassium acetate, CH3COOK, to 1.00 L of water. Which statement about the solution is correct? a. The solution is acidic. b. The concentration of acetate ions will be greater than the concentration of potassium ions c. The concentrations of potassium ions and acetate ions will be identical. d. The solution is basic. e. The solution is neutral. 26. Which of the following reactions would occur to a measurable extent in water? a. HSO4 (aq) + H2O(l) H2SO4(aq) + HO (aq) b. NO3 (aq) + H2O(l) HNO3(aq) + HO (aq) c. NH4 + (aq) + H2O(l) H3O + (aq) + NH3(aq) d. All the above would occur to a measurable extent in water e. Only a and c would occur to a measurable extent in water Key 1. B 2. C 3. C 4. B 5. B 6. C 7. C 8. E 9. D 10. B 11. C 12. E 13. E 14. C 15. A 16. D 17. C 18. B 19. D 20. C 21. A 22. E 23. A 24. A 25. D 26. C It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 6 of 6