Test Bank For Organic Chemistry, 7th Edition

Organic Chemistry, 7e (Bruice) Chapter 2 Acids and Bases: Central to Understanding Organic Chemistry 1) Which of the following is not a conjugate acid-base pair? A) H2O, HOB) H2O, H3O+ C) HSO4-, H2SO4 D) -OH, O2E) NO3-, NO2Answer: E Section: 2-1 2) What is the product formed from the following acid-base reaction when ammonia functions as a base? The equilibrium lies far to the reactants. A) CH3O- + +NH4 B) CH2OH + +NH3 C) CH3OH2+ + -NH2 D) CH3NH2 + H2O E) CH4 + NH2OH Answer: A Section: 2-1 3) The conjugate acid of H2O is ________. A) H3OB) H3O C) H3O+ D) HOE) H2O+ Answer: C Section: 2-1 4) Which of the following ions is the strongest acid? A) HB) HOC) HSO4D) H2O E) H3O+ Answer: E Section: 2-1 1 5) Which species act as bases in the following reaction? A) 1 and 2 B) 3 and 4 C) 2 and 4 D) 1 and 3 E) 2 and 3 Answer: C Section: 2-1 6) What is the conjugate acid of NH3? A) +NH3 B) -NH C) +NH4 D) -NH2 E) +NH2 Answer: C Section: 2-1 7) What is the conjugate acid of CH3NH2? A) CH3NH3+ B) CH3NHC) NH4+ D) NH2Answer: A Section: 2-1 8) What is the conjugate base of CH3NH2? A) CH3NH3+ B) CH3NHC) NH4+ D) NH2Answer: B Section: 2-1 2 9) Give the conjugate acid and the conjugate base for HSO4-. Answer: conjugate acid: H2SO4 conjugate base: SO42Section: 2-1 10) Write a completed equation for the acid-base pair shown below. HCO2H + -NH2 → Answer: HCO2H + -NH2 → HCO2- + NH3 Section: 2-1 11) What is the pH of a 0.1 M solution of HCl? (Note: pKa for HCl is -6.) A) 6 B) -6 C) 1 D) -8 E) -1 Answer: C Section: 2-2 12) If H2O has a pKa value of 15.7 and HF has a pKa value of 3.2, which is a stronger base, HOor F-? Explain. Answer: HO- is a stronger base than F- because HF is a stronger acid than H2O, and the stronger the acid the weaker its conjugate base. Section: 2-2 13) 2-Propanol is shown below. Draw the structure of its conjugate base. (CH3)2CHOH Answer: Section: 2-3 3 14) Which of the following is the strongest acid? A) CH3OH B) CH3OH2+ C) H2ND) CH3NH2 E) CH3NH3+ Answer: B Section: 2-6 15) The pKa of CH3COOH is 4.8 and the pKa of HCOOH is 3.8. Given this information, one knows that ________. A) CH3COOH completely ionizes in water B) HCOOH is a weaker acid than CH3COOH C) HCOO- is a weaker base than CH3COOD) CH3COOH reacts with HO- while HCOOH does not E) HCOOH reacts with HO- while CH3COOH does not Answer: C Section: 2-6 16) Which of the following is the strongest acid? A) HF B) H2O C) : NH3 D) CH4 E) CH3OH Answer: A Section: 2-6 17) Which of the following is the strongest acid? A) CH3CH2OH B) CH3OCH3 C) CH3—NH—CH3 D) CH3—C CH E) CH3—CH CH2 Answer: A Section: 2-6 4 18) Consider the set of compounds, NH3, HF, and H2O. Rank these compounds in order of increasing acidity and discuss your rationale. Answer: NH3 < H2O [CH3COO-] C) [CH3COOH] = [CH3COO-] D) [CH3COOH] < [CH3COO-] E) CH3COOH is completely unionized Answer: C Section: 2-10 28) When a small amount of hexanoic acid [CH3(CH2)4CO2H, pKa~4.8], is added to a separatory funnel which contains the organic solvent diethyl ether and water with a pH of 2.0, it is found mainly in the ________ phase as ________. A) ether; CH3(CH2)4CO2B) water; CH3(CH2)4CO2C) ether; CH3(CH2)4CO2H D) water; CH3(CH2)4CO2H E) none of the above Answer: C Section: 2-10 29) When a small amount of hexanoic acid [CH3(CH2)4CO2H, pKa~4.8], is added to a separatory funnel which contains the organic solvent diethyl ether and water with a pH of 12.0, it is found mainly in the ________ phase as ________. A) ether; CH3(CH2)4CO2B) water; CH3(CH2)4CO2C) ether; CH3(CH2)4CO2H D) water; CH3(CH2)4CO2H E) none of the above Answer: B Section: 2-10 7 30) At what pH will 25% of a compound with a pKa of 5.3 be in its basic form? Answer: 4.8 Section: 2-10 31) The amino acid glycine (H3N+CH2CO2H) has two acidic Hs, one with pKa = 2.34 and the other with pKa=9.60. Draw the structure of the form of glycine that predominates at a pH of 12. Answer: Section: 2-10 32) H-A is an acid with a pKa of 4.5. Which of the following statements about an aqueous solution of H-A is true? A) At pH = 4.5, the solution contains much more H-A than AB) At pH = 4.5, the solution contains much more A- than H-A C) At pH- 3.5, the solution contains about 90% A- and 10% H-A D) At pH = 6.5, the soluton contains about 80% A- and 20% H-A E) At pH = 5.5, the solution contains about 90% A- and 10% H-A Answer: E Section: 2-10 33) At what pH will the concentration of a compound with a pKa of 5.7 be 100 times greater in its acidic form than in its basic form? Answer: 3.7 Section: 2-10 34) HCN has a pKa = 9.1. What form of the compound, HCN or CN-, will predominate in a solution of pH = 7.0 Answer: HCN Section: 2-10 35) Propanoic acid, CH3CH2COOH, has a pKa =4.9. Draw the structure of the conjugate base of propanoic acid and give the pH above which 90% of the compound will be in this conjugate base form. Answer: CH3CH2COO-; 5.9 Section: 2-10 8 36) Buffering is used to maintain the pH of human blood in the relatively narrow 7.3 – 7.4 range. What acid/base pair serves to buffer the blood? A) H2O / HOB) H3O+ / H2O C) H2CO3 / HCO3D) NH4+ / NH3 E) HCl / ClAnswer: C Section: 2-11 37) Explain why AlCl3 is a Lewis acid. Answer: A Lewis acid is an electron pair acceptor. Aluminum in AlCl3 has an empty p orbital that can accommodate the pair of electrons provided by a Lewis base. Section: 2-12 9