Solutions are aqueous and the temperature is 25 C unless stated otherwise.

Transcription

1 Solutions are aqueous and the temperature is 25 C unless stated otherwise. 1. According to the Arrhenius definition, an acid is a substance that produces ions in aqueous solution. A. H C. OH B. H + D. OH + 2. Consider the reaction CH 3 NH 2 (aq) + HNO 2 (aq) CH 3 NH 3 + (aq) + NO 2 (aq) The substance CH 3 NH 2 is (1) according to the Brønsted-Lowry definition because it is (2) in the reaction. A. (1) a base; (2) a proton acceptor B. (1) a base; (2) an electron pair donor C. (1) an acid; (2) a proton donor D. (1) an acid; (2) an electron pair acceptor 3. The ph values of solutions of four monoprotic acids (HA, HB, HC and HD) are listed below. Which acid has the largest K a value? Solution ph 1.00 M HA M HB M HC M HD 3.4 A. HA C. HC B. HB D. HD

2 4. Choose the false statement concerning a solution with [H 3 O + ] = A. poh = 5.53 C. [OH ] = B. ph =14.00 poh D. The solution is acidic 5. What is [OH ] of an aqueous solution at 25 ºC if [H 3 O + ] = M? A M C M B M D M 6. is a weak acid; is a strong acid. A. HNO 2 ; HClO 4 C. HC 2 H 3 O 2 ; HNO 2 B. HNO 3 ; HC 2 H 3 O 2 D. HClO 4 ; HI 7. The ph of a M HCl(aq) solution is. The ph of a M CH 3 COOH(aq) solution is. A. ph = 2.00, ph < 2.00 C. ph = 2.00, ph > 2.00 B. ph = 2.00, ph = 2.00 D. ph < 2.00, ph > 2.00

3 8. Calculate the ph of a 0.18 M HNO 2 solution. K a (HNO 2 ) = A C B D What is the percent ionization of a M solution of benzoic acid (monoprotic)? K a of benzoic acid = A % C. 1.6% B % D. 3.2% 10. Calculate the ph of a solution containing M HBr and M HC 7 H 5 O 2 (benzoic acid). K a (benzoic acid) = A C B D Select the solution with the highest ph. A M HCl C M HBr B M HF D. A and C are equally the highest.

4 12. What is the K b value for CHO 2 given that the K a of HCHO 2 is ? A C B D For methylamine (CH 3 NH 2 ), K b is Select the correct values. A. pk b (CH 3 NH 2 ) = 3.36, pk a (CH 3 NH 3+ ) = B. pk b (CH 3 NH 2 ) = 4.44, pk a (CH 3 NH + 3 ) = 4.44 C. pk b (CH 3 NH 2 ) =3.36, pk a (CH 3 NH 3+ ) = 3.36 D. pk b (CH 3 NH 2 ) = 4.44, pk a (CH 3 NH + 3 ) = The ph of a 0.10 M solution is given for each of the following bases. Select the base with the largest K b value. A. aniline, ph = 8.79 B. pyridine, ph = 9.12 C. ethylamine, ph = D. The formula of the base must be known to determine the answer.

5 15. What is the ph of a M NaF solution? K a of HF = A C B D Which M salt solution will result in the lowest ph? A. CH 3 NH 3 I C. KC 2 H 3 O 2 B. NaNO 3 D. RbClO The autoionization constant of water (K w ) depends on temperature. At 0 C, the ph of neutral water is What is K w of water at 0 C? A B C D

6 18. Which pair has the stronger acid listed first? A. H 2 Te, H 2 S C. H 2 O, H 2 Se B. H 2 O, HF D. H 2 S, HCl 19. Which oxyacid has the smallest K a? A. HNO 3 C. HBrO 3 B. HClO 3 D. HIO Which substance can act as a Lewis acid? A. NH 3 C. O 2 B. Pt 4+ D. Br 21. Consider the bond, designated by an arrow, on the product side of the reaction. Select the true statement. A. The bond is formed as aluminum trichloride (the Lewis base) donates electrons to diethyl ether (the Lewis acid). B. The bond is formed as aluminum trichloride (the Lewis acid) donates electrons to diethyl ether (the Lewis base). C. The bond is formed as diethyl ether (the Lewis base) donates electrons to aluminum trichloride (the Lewis acid). D. The bond is formed as diethyl ether (the Lewis acid) donates electrons to aluminum trichloride (the Lewis base).

7 22. Which statement about buffers is false? A. A solution containing significant amounts of a weak acid and its conjugate base is a buffer. B. A solution containing significant amounts of a weak base and its conjugate acid is a buffer. C. A buffer resists ph changes when the weak acid in the buffer neutralizes an added base. D. A buffer resists ph changes when the weak acid in the buffer neutralizes an added acid. 23. Which pair acts as a buffer when an equimolar amount of each compound is mixed together in an aqueous solution? A. HCl and NaCl C. H 2 SO 4 and SO 4 2 B. NH 3 and NH 4 + D. H 2 O and HF 24. Calculate the ph of a buffer containing 0.18 M CH 3 NH 2 and 0.12 M CH 3 NH 3 Br. K b (CH 3 NH 2 ) = A C B D

8 25. Calculate the ph of a buffer containing M HNO 2 and M KNO 2. K a (HNO 2 ) = A C B D A buffer is prepared from a mixture of 100 ml of M acetic acid and enough sodium acetate that the ph is If 10 ml of M HCl is added, what happens to the ph? A. The ph increases by more than two ph units. B. The ph increases by less than two ph units. C. The ph decreases by more than two ph units. D. The ph decreases by less than two ph units. 27. Calculate the ph of a solution formed when moles of HCl are added to ml of a 0.10 M NaNO 2 /0.10 M HNO 2 buffer. K a (HNO 2 ) = A C B D. 2.20

9 28. Which solution makes the least effective formic acid (HCHO 2 ) buffer? A M HCHO 2, M KCHO 2 B M HCHO 2, M KCHO 2 C M HCHO 2, M KCHO 2 D M HCHO 2, M KCHO Which buffer solution is the least effective against the addition of moles of HCl? A moles HA, moles of A B moles HA, moles of A C moles HA, moles of A D moles HA, moles of A mol of NaCN is added to 10.0 L of a solution containing 0.10 M NaNO 2 and 0.12 M HNO 2. Which statement is correct? A. Because CN reacts with and is neutralized by the HNO 2 of the buffer, the ph changes only minimally. B. Because Na + reacts with and is neutralized by the NO 2 of the buffer, the ph changes only minimally. C. Because buffers cannot neutralize salts, the addition of NaCN causes the ph to decrease substantially. D. Because the solution is not a buffer, the addition of NaCN causes the ph to increase substantially.

10 Answer Key: 1. B 2. A 3. C 4. D 5. A 6. A 7. C 8. B 9. C 10. D 11. B 12. A 13. A 14. C 15. C 16. A 17. C 18. A 19. D 20. B 21. C 22. D 23. B 24. D 25. B 26. D 27. C 28. B 29. C 30. A