Amino acids are building blocks of proteins. These compounds contain at least one amino group
Fully protonated: -
Dipolar ion:
Fully ionized:
Predict the predominant form of glycine at pH 1.0, 7.0. and 12.0. The
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- Ionization of the first proton from H2SO4 is complete (H2SO4 is a strong acid); the acid-ionization constant for the second proton is 1.1 102. a What would be the approximate hydronium-ion concentration in 0.100 M H2SO4 if ionization of the second proton were ignored? b The ionization of the second proton must be considered for a more exact answer, however. Calculate the hydronium-ion concentration in 0.100 M H2SO4, accounting for the ionization of both protons.arrow_forwardMalic acid is a weak diprotic organic acid with Ka1 = 4.0 104 and Ka2 = 9.0 105. a Letting the symbol H2A represent malic acid, write the chemical equations that represent Ka1 and Ka2. Write the chemical equation that represents Ka1 Ka2. b Qualitatively describe the relative concentrations of H2A, HA, A2, and H3O+ in a solution that is about one molar in malic acid. c Calculate the pH of a 0.0175 M malic acid solution and the equilibrium concentration of [H2A]. d What is the A2 concentrationin in solutions b and c?arrow_forwardIonization of the first proton from H2SeO4 is complete (H2SeO4 is a strong acid); the acid-ionization constant for the second proton is 1.2 102. a What would be the approximate hydronium-ion concentration in 0.150 M H2SeO4 if ionization of the second proton were ignored? b The ionization of the second proton must be considered for a more exact answer, however. Calculate the hydronium-ion concentration in 0.150 M H2SeO4, accounting for the ionization of both protons.arrow_forward
- Table 13-4 lists the stepwise Ka values for some polyprotic acids. What is the difference between a monoprotic acid, a diprotic acid, and a triprotic acid? Most polyprotic acids are weak acids; the major exception is H2SO4. To solve for the pH of a solution of H2SO4, you must generally solve a strong acid problem as well as a weak acid problem. Explain. Write out the reactions that refer to Ka1 and Ka2 for H2SO4. For H3PO4, Ka1 = 7.5 103, Ka2 = 6.2 108, and Ka3= 4.8 1013. Write out the reactions that refer to the Ka1, Ka2and Ka3equilibrium constants. What are the three acids in a solution of H3PO4? Which acid is strongest? What are the three conjugate bases in a solution of H3PO4? Which conjugate base is strongest? Summarize the strategy for calculating the pH of a polyprotic acid in water.arrow_forwardStrong Acids, Weak Acids, and pH Two 0.10-mol samples of the hypothetical monoprotic acids HA(aq) and HB(aq) are used to prepare 1.0-L stock solutions of each acid. a Write the chemical reactions for these acids in water. What are the concentrations of the two acid solutions? b One of these acids is a strong acid, and one is weak. What could you measure that would tell you which acid was strong and which was weak? c Say that the HA(aq) solution has a pH of 3.7. Is this the stronger of the two acids? How did you arrive at your answer? d What is the concentration of A(aq) in the HA solution described in part c? e If HB(aq) is a strong acid, what is the hydronium-ion concentration? f In the solution of HB(aq), which of the following would you expect to be in the greatest concentration: H3O+(aq), B(aq), HB(aq), or OH(aq)? How did you decide? g In the solution of HA(aq), which of the following would you expect to be in the greatest concentration: H3O+(aq), A+(aq), HA(aq), or OH(aq)? How did you decide? h Say you add 1.0 L of pure water to a solution of HB. Would this water addition make the solution more acidic, make it less acidic, or not change the acidity of the original solution? Be sure to fully justify your answer. i You prepare a 1.0-L solution of HA. You then take a 200-mL sample of this solution and place it into a separate container. Would this 200 mL sample be more acidic, be less acidic, or have the same acidity as the original 1.0-L solution of HA(aq)? Be sure to support your answer.arrow_forwardAt 25 C, a 0.10% aqueous solution of adipic acid, C5H9O2COOH, has a pH of 3.2. A saturated solution of the acid, which contains 1.44 g acid per 100. mL of solution, has a pH = 2.7. Calculate the percent dissociation of adipic acid in each solution.arrow_forward
- A quantity of 0.25 M sodium hydroxide is added to a solution containing 0.15 mol of acetic acid. The final volume of the solution is 375 mL and the pH of this solution is 4.45. a What is the molar concentration of the sodium acetate? b How many milliliters of sodium hydroxide were added to the original solution? c What was the original concentration of the acetic acid?arrow_forwardAn aqueous solution contains formic acid and formate ion. Determine the direction in which the pH will change if each of the following chemicals is added to the solution. (a) HCl (b) NaHSO4 (c) CH3COONa (d) KBr (e) H2Oarrow_forwardA solution made up of 1.0 M NH3 and 0.50 M (NH4)2SO4 has a pH of 9.26. a Write the net ionic equation that represents the reaction of this solution with a strong acid. b Write the net ionic equation that represents the reaction of this solution with a strong base. c To 100. mL of this solution, 10.0 mL of 1.00 M HCl is added. How many moles of NH3 and NH4+ are present in the reaction system before and after the addition of the HCl? What is the pH of the resulting solution? d Why did the pH change only slightly upon the addition of HCl?arrow_forward
- The pigment cyanidin aglycone is one of the anthocyanin molecules that gives red cabbage (Brassica oleracea var. capitata f. rubra) its characteristic red coloration. Many chemistry students have used this red cabbage indicator to study acid-base chemistry. Estimate tire pH range at which cyanidin agly-cone shows a color change. Anth-H(aq) Anth(aq) + H+ (aq) Ka = 1.3 107arrow_forwardA quantity of 0.15 M hydrochloric acid is added to a solution containing 0.10 mol of sodium acetate. Some of the sodium acetate is converted to acetic acid, resulting in a final volume of 650 mL of solution. The pH of the final solution is 4.56. a What is the molar concentration of the acetic acid? b How many milliliters of hydrochloric acid were added to the original solution? c What was the original concentration of the sodium acetate?arrow_forwardComposition diagrams, commonly known as alpha plots, are often used to visualize the species in a solution of an acid or base as the pH is varied. The diagram for 0.100 M acetic acid is shown here. The plot shows how the fraction [alpha ()] of acetic acid in solution, =[CH3CO2H][CH3CO2H]+[CH3CO2] changes as the pH increases (blue curve). (The red curve shows how the fraction of acetate ion, CH3CO2, changes as the pH increases.) Alpha plots are another way of viewing the relative concentrations of acetic acid and acetate ion as a strong base is added to a solution of acetic acid in the course of a titration. (a) Explain why the fraction of acetic acid declines and that of acetate ion increases as the pH increases. (b) Which species predominates at a pH of 4, acetic acid or acetate ion? What is the situation at a pH of 6? (c) Consider the point where the two lines cross. The fraction of acetic acid in the solution is 0.5, and so is that of acetate ion. That is, the solution is half acid and half conjugate base; their concentrations are equal. At this point, the graph shows the pH is 4.74. Explain why the pH at this point is 4 74.arrow_forward
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