Choose the correct structure for thiamine hydrochloride at pH 10. a H₂C H₂C P A b B C C N D NH₂ NH₂ CI- A CI- C CH3 CH3 HCI -OH H₂C e more than one structure is correct H₂C N NH3 Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. NH₂ CI- D CH3 CH3 S HCI -OH OH

Choose the correct structure for thiamine hydrochloride at pH 10. a H₂C H₂C P A b B C C N D NH₂ NH₂ CI- A CI- C CH3 CH3 HCI -OH H₂C e more than one structure is correct H₂C N NH3 Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. NH₂ CI- D CH3 CH3 S HCI -OH OH

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter15: Complex Acid/base Systems

Section: Chapter Questions

Problem 15.16QAP

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Use Table 13-2 to order the following from the strongest to the weakest acid. HClO2,H2O,NH4+,HClO4
16-27 Guanidine, p/Ca 13.6, is a very strong base, almost as basic as hydroxide ion. NH NH2+ II II H2N—C—NH2 + H2O H2N—C—NH2 + OH" Guanidine Guanidinium ion pKb = 13.6 Complete the Lewis structure for guanidine, showing all valence electrons. The remarkable basicity of guanidine is attributed to the fact that the positive charge on the guanidinium ion is delocalized by resonance over the three nitrogen atoms. This delocalization increases the stability of the guanidinium ion relative to the ammonium ion or substituted ammonium ions. Draw three equivalent contributing structures for the guanidinium ion and show by the use of curved arrows how these three contributors are related. Propose an explanation for the fact that protonation occurs on the C=NH nitrogen rather than on one of the —NH., nitrogens. (Hint: Consider the resonance stabilization of the structure formed by protonation on a —NH., nitrogen compared with the resonance stabilization of the structure formed by protonation on the =NH nitrogen.) Predict the N—C—N bond angles in the hybrid. Which is the stronger acid, the ammonium ion or the guanidinium ion?
Calculate the percentages of dissociated and undissociated forms present in the following solutions: (a) 0.0010 M glycolic acid (HOCH2CO2H; pKa = 3.83) at pH = 4.50 (b) 0.0020 M propanoic acid (pKa = 4.87) at pH = 5.30
The following reactions illustrate Brnsted acid-base behavior. Complete each equation. a.HI(aq)+?H3O+(aq)+I(aq) b.NH3(l)+?NH4++NH2 c.H2C2O4(aq)+H2O(l)?+HC2O4(aq) d.H2N2O2(aq)+H2O(l)H3O+(aq)+? e.?+H2O(l)H3O+(aq)+CO32(aq)
Salicylic acid, HOC6H4CO2H, and its derivatives have been used as pain relievers for a long time. Salicylic acid occurs in small amounts in the leaves, bark, and roots of some vegetation (most notably historically in the bark of the willow tree). Extracts of these plants have been used as medications for centuries. The acid was first isolated in the laboratory in 1838. (a) Bath functional groups of salicylic acid ionize in water, with Ka=1.0103 for the—CO2H group and 4.201013 for the -OH group. What is the pH of a saturated solution of the acid (solubility = 1.8 g/L).. (b) Aspirin was discovered as a result of efforts to produce a derivative of salicylic acid that would not be irritating to the stomach lining. Aspirin is acetylsalicylic acid, CH3CO2C6H4CO2H. The -CO2H functional group is still present, but its acidity is reduced, Ka=3.0104. What is the pH of a solution of aspirin with the same concentration as a saturated solution of salicylic acid (See Part a). (c) Under some conditions, aspirin reacts with water and forms a solution of salicylic acid and acetic acid: CH3CO2C6H4CO2H(aq)+H2O(l)HOC6H4CO2H(aq)+CH3CO2H(aq) i. Which of the acids, salicylic acid or acetic acid, produces more hydronium ions in such a solution? ii. What are the concentrations of molecules and ions in a solution produced by the hydrolysis of 0.50 g of aspirin dissolved in enough water to give 75 mL of solution?