Concept explainers
The Henderson-Hasselbalch equation can be written as
a. Use this equation to plot the pH versus tie degree of ionization for me second ionization constant of phosphoric acid
b. If
c. If the solution had a pH of 6.0, what would the value of a be?
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EBK GENERAL CHEMISTRY
- The simplest amino acid is glycine, H2NCH2CO2H. The common feature of amino acids is that they contain the functional groups: an amine group, -NH2, and a carboxylic acid group, -CO2H. An amino acid can function as either an acid or a base. For glycine, the acid strength of the carboxyl group is about the same as that of acetic acid. CH3CO2H, and the base strength of the amino group is slightly greater than that of ammonia, NH3. (a) Write the Lewis structures of the ions that form when glycine is dissolved in 1 M HCl and in 1 M KOH. (b) Write the Lewis structure of glycine when this amino acid is dissolved in water. (Hint: Consider the relative base strengths of the -NH2 and -CO2- groups.)arrow_forwardThe 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_forwardWrite the chemical equation and the expression for the equilibrium constant, and calculate Kb for the reaction of each of the following ions as a base. (a) sulfate ion (b) citrate ionarrow_forward
- Amino acids are an important group of compounds. At low pH, both the carboxylic acid group (CO2H) and the amine group (NHR) are protonated. However, as the pH of the solution increases (say, by adding base), the carboxylic acid proton is removed, usually at a pH between 2 and 3. In a middle range of pHs, therefore, the amine group is protonated, but the carboxylic acid group has lost the proton. (This is called a zwitterion.) At more basic pH values, the amine proton is dissociated. What is the pH of a 0.20 M solution of alanine hydrochloride, [NH3CHCH3CO2H]Cl?arrow_forwardThe concentration of acetylcholine (a neurotransmitter) in a sample can be determined from the pH changes that accompany its hydrolysis. When the sample is incubated with the enzyme acetylcholinesterase, acetylcholine is converted to choline and acetic acid, which dissociates to yield acetate and a hydrogen ion. CНз CHз Нао — сHz— CH "N— снз но-сн— сH,-"N-CH; + CH;— с-о+ н* CH3-C-0- сHз CHз Choline Acetylcholine Acetate In a typical analysis, 11 mL of an aqueous solution containing an unknown amount of acetylcholine had a pH of 7.70. When incubated with acetylcholinesterase, the pH of the solution decreased to 6.89. Assuming there was no buffer in the assay mixture, determine the number of moles of acetylcholine in the 11 mL sample.arrow_forwardPropanoic acid, CH₂CH₂COOH, is a weak monoprotic acid that is used to inhibit mould formation in bread. A student prepared a 0.10 mol/L solution of propanoic acid and found that the pH was 2.96. What is the acid dissociation constant for propanoic acid? [Hint: Setup an I.C.E. table] CH3CH₂COOH (aq) Ka for propanoic acid is: ←CH3CH₂COO (aq) + H (aq)arrow_forward
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- An acid-base equilibrium system is created by dissolving 0.50 mol CH3CO2H in water to a volume of 1.0 L. What is the effect of adding 0.50 mol CH3CO2–(aq) to this solution? 1.The pH of the solution will equal 7.00 because equal concentrations of a weak acid and its conjugate base are present. 2.Some CH3CO2H(aq) will ionize, increasing the concentration of CH3CO2–(aq) and increasing the pH.3.Some CH3CO2–(aq) will react with H3O+, increasing the concentration of CH3CO2H(aq) and reestablishing the solution equilibrium. b. 2 only c. 3 only d. 1 and 3 e. 1, 2, and 3arrow_forwardCalculate the pH of a 1.00 L solution of 0.100 M NH 3(aq) after the addition of 0.010 mol NH 4Cl(s). For NH 3, pK b = 4.74.arrow_forward
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