(a)
Interpretation:
The pH at which the zwitter ion [Z] and the cationic form [C+] of the amino acid alanine become equal needs to be calculated.
Concept introduction:
- Amino acids are organic compounds composed of C, H, N and O. The two main
functional groups include the amino −NH2 and carboxyl −COOH group in addition to a side chain each with a characteristic pKa value. - Isoelectric point (pI) is the pH at which the net charge on the amino acid is zero. For amino acid with one −COOH and one −NH2, the pI is given as:
Answer to Problem 30QAP
pH = 2.29
Explanation of Solution
The given amino acid is alanine which has the following structure:
The structures of the respective cationic form (C+), zwitter ion (Z) and the anionic form (A-) are:
The acid-base equilibria for alanine involving the cation and the zwitter ion forms is:
(b)
Interpretation:
The pH at which the zwitter ion [Z] and the anionic form [A-] of the amino acid alanine become equal needs to be calculated
Concept introduction:
- Amino acids are organic compounds composed of C, H, N and O. The two main functional groups include the amino −NH2 and carboxyl −COOH group in addition to a side chain each with a characteristic pKa value.
- Isoelectric point (pI) is the pH at which the net charge on the amino acid is zero. For amino acid with one −COOH and one −NH2, the pI is given as:
Answer to Problem 30QAP
pH = 9.74
Explanation of Solution
The given amino acid is alanine which has the following structure:
The structures of the respective cationic form (C+), zwitter ion (Z) and the anionic form (A-) are:
The acid-base equilibria for alanine involving the anion and the zwitter ion forms is:
(c)
Interpretation:
The pH at the isoelectric point needs to be calculated
Concept introduction:
- Amino acids are organic compounds composed of C, H, N and O. The two main functional groups include the amino −NH2 and carboxyl −COOH group in addition to a side chain each with a characteristic pKa value.
- Isoelectric point (pI) is the pH at which the net charge on the amino acid is zero. For amino acid with one −COOH and one −NH2, the pI is given as:
Answer to Problem 30QAP
pH = 6.02
Explanation of Solution
For alanine at the isoelectric point:
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Chapter 23 Solutions
Chemistry: Principles and Reactions
- Apatite, Ca5(PO4)3OH, is the mineral in teeth. On a chemical basis explain why drinking milk strengthens young children’s teeth. Sour milk contains lactic acid. Not removing sour milk from the teeth of young children can lead to tooth decay. Use chemical principles to explain why.arrow_forward(b) Calculate the pH of 0.0005 mol dm-3 ethanoic acid when its pKa = 4.75 and explain the assumptions made in the calculations CH3COOH(aq) CH3COO-(aq) + H+(aq) Ka = pH =arrow_forwardIf Phenolphthalein was added to H2O (l) + CO2 (g) → H2CO3 (aq) what color would the solution be?arrow_forward
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- Predict the products from the following chemical reactions. (a) HNO3 + Ba(OH)2 ⟶ (b) CaCl2 + CsOH ⟶ (c) Ammonium Phosphate + Magnesium Sulfate ⟶arrow_forward(f) Calculate the pH of the following solutions: (i) A 0.045 M solution of sulphuric acid. (ii) A solution containing 0.4 g sodium hydroxide in 100 cm³ water. (iii) Given the Ka value for CH3COOH is 1.8 x 10-5, calculate the pH of the acid. The initial concentration of the acid is 0.2 Marrow_forwardA monoprotic weak acid,HA, dissociates in water according to the reaction HA(aq)+H2O equilibrium arrows H3O+(aq)+A-(aq) The equilibrium concentrations of the reactants and products are [HA]=0.230M, [H3O+]=4.00•10^-4 and [A-]=4.00•10^-4. Calculate the Ka value for the acid HA.arrow_forward
- Chemistry: Principles and ReactionsChemistryISBN:9781305079373Author:William L. Masterton, Cecile N. HurleyPublisher:Cengage LearningChemistry: The Molecular ScienceChemistryISBN:9781285199047Author:John W. Moore, Conrad L. StanitskiPublisher:Cengage Learning