BCBP 4760 Molecular Biochemistry 1 - Chapter 2 - The Chemistry Of Water: WileyPlus Homework

Which best describes the buffering range of phosphoric acid? A) pH = 2.15, 6.82, 12.38 B) pH = 1.15-3.15, 5.82-7.82, 11.38-13.38 C) pH = 2.15-12.38 D) pH = 1.15-13.38

pH = 1.15-3.15, 5.82-7.82, 11.38-13.38 The effective buffering range of phosphoric acid is given by each pK +/- 1

Which of the following statements is not true? A) Acetic acid (pK = 4.76) is an effective buffer against acid at pH 5.76. B) Acetic acid (pK = 4.76) is an effective buffer against acid at pH 3.76. C) Ammonium hydroxide (pK = 9.25) is an effective buffer against base at pH 8.25. D) Ammonium hydroxide (pK = 9.25) is an effective buffer against base at pH 9.75

Acetic acid (pK = 4.76) is an effective buffer against acid at pH 3.76 An acid will drive the buffer out of its buffering range at pH 3.76. It is only effective against an acid at pH 5.76

Which of the following statements is not true? A) Ammonium hydroxide (pK = 9.25) is not an effective buffer against acid or hydroxide at pH 7.75. B) Ammonium hydroxide (pK = 9.25) is an effective buffer against acid at pH 8.25. C) Ammonium hydroxide (pK = 9.25) is an effective buffer against acid at pH 10.25. D) Ammonium hydroxide (pK = 9.25) is an effective buffer against acid or hydroxide at pH 9.25.

Ammonium hydroxide (pK = 9.25) is an effective buffer against acid at pH 8.25

Which of the following functional groups could NOT act as a hydrogen bond donor? A) An amino group. B) An aldehyde. C) A hydroxyl group. D) Both aldehyde and ester. E) An ester.

Both aldehyde and ester

Which of the following correctly lists bonding interactions in terms of their increasing strength: A) Van der Waals interactions<ionic interactions<hydrogen bonding<covalent bonds B) Hydrogen bonds<ionic interactions<covalent interactions<Van der Waals interactions C) Covalent bonds<hydrogen bonds<ionic interactions<Van der Waals interactions D) Van der Waals interactions<hydrogen bonding<ionic interactions<covalent bonds

Van der Waals interactions<hydrogen bonding<ionic interactions<covalent bonds

Which of the properties listed is NOT true of liquid water? A) Liquid water tends to form hydrogen bonded rings of three to seven molecules. B) Liquid water consists of a rapidly fluctuating, three-dimensional network of hydrogen-bonded molecules. C) Liquid water is only 15% less hydrogen bonded than ice at 0o C. D) Liquid water is less dense than ice.

Liquid water is less dense than ice The density of ice is 0.92g/mL whereas the density of water is 1.0g/mL

Which of the following statements is not accurate when considering water and biological molecules? A) Water can act as a hydrogen bond acceptor. B) Polar substances are soluble because of their interaction with water. C) Non-polar substances associate with water to maximize their exposed surface area. D) Water can act as a hydrogen bond donor.

Non-polar substances associate with water to maximize their exposed surface area

From the pK's in table 2-4, considering all other factors equal, which weak acid/conjugate base pair will give the best buffer for a pH of 4.3? A) acetic acid/acetate- B) oxalic acid/oxalate- C) succinic acid/succinate- D) succinate-/ succinate2-

Succinic Acid/Succinate- Succinic acid has a pK of 4.21, thus giving succinct acid/succinate- a buffering range of pH 3.21-5.21. Since 4.21 is closest to 4.3, this pair will have the greatest buffering capacity at pH 4.3

Which of the following statements is not accurate when considering water and biological molecules? A) Water is more likely to act as a hydrogen bond donor than a hydrogen bond acceptor. B) Polar substances are soluble because of their interaction with water. C) The hydrogen bonding pattern of water is disrupted by the presence of hydrophobic molecules.

Water is more likely to act as a hydrogen bond donor than a hydrogen bond acceptor

What is the pH of 1 M NaOH? A) 15 B) 14 C) 1 D) 13

14 [NaOH] = 1 M - 10^0 pOH = -log[NaOH

What is the pH of a solution made by mixing equal volumes of 1 M sodium acetate and 1 M acetic acid? A) 1 B) 3.76 C) 4.76 D) 5.76

4.76 pH = 4.76 + log(1/1) pH = 4.76 + 0 pH = 4.76

What is the pH of a solution made by mixing equal volumes of 1 M sodium acetate and 0.1 M acetic acid? (The pK of acetic acid is 4.76. A) 4.66 B) 3.76 C) 5.76 D) 4.86

5.76 pH = pK + log([A-]/[HA]) pH = 4.76 + log(1/0.1) pH = 5.76

Rank the following bond/interaction distances correctly in order from shortest to longest: A) Van der Waals interactions, covalent bond, hydrogen bond. B) Van der Waals interactions, hydrogen bond, covalent bond. C) Covalent bond, van der Waals interactions, hydrogen bond. D) Covalent bond, hydrogen bond, van der Waals interactions. E) Hydrogen bond, van der Waals interactions, covalent bond.

Covalent bond, hydrogen bond, van der Waals interactions.

Which statement best explains why water can solvate both negative and positive ions? A) It is very small. B) It can ionize. C) It can hydrogen bond. D) It is dipolar.

It is dipolar

Consider a solution separated from pure water by a semipermeable membrane that permits the passage of water, but not solutes. Which statement is false? A) Osmosis is the movement of solvent from a region of high solvent concentration to a solution of lower solvent concentration. B) Osmotic pressure could be eliminated if enough solute were added to the region of pure water. C) Osmotic pressure depends upon the size of the solute molecules. D) Osmotic pressure is the pressure that must be applied to the solution to prevent the inflow of water.

Osmotic pressure depends upon the size of the solute molecules

Which of the following statements about the buffering system in blood in not true? A) The buffering capacity of blood depends primarily on two equilibria: The first, CO2 + H2O H2CO3 and the second, H2CO3 H+ + HCO3-, where the overall pK for these two sequential reactions is 5.35. B) Alkalosis is a medical condition where the pH of blood rises above normal. Hyperventilation accelerates the loss of CO2 and causes respiratory alkalosis, which can be ameliorated by breathing in an atmosphere enriched in CO2. C) The most significant buffering compound in human blood is bicarbonate (HCO3-). D) Blood is buffered so that it maintains a pH of 7.4.

The buffering capacity of blood depends primarily on two equilibria: The first, CO2 + H2O H2CO3 and the second, H2CO3 H+ + HCO3-, where the overall pK for these two sequential reactions is 5.35 Blood is buffered at a pH of 7.4. Therefore the buffering range is pK 6.4-8.4; therefore a buffer with a pK of 5.35 would not be suitable to buffer blood at a pH of 7.4

Why are the ionic mobilities of H+ and OH- in an aqueous environment much greater than that of other ions? A) They have less mass than other ions. B) They have unit charge. C) The hydrogen ion can hop from one water molecule to another. D) They are smaller than most other ions.

The hydrogen ion can hop from one water molecule to another

Which of the following statements about water is FALSE? A) The hydrophobic effect is driven largely by the entropy of the non-polar substance. B) Substances with polar functional groups are generally soluble in water. C) Water carries a dipole because of the geometry of the two oxygen-hydrogen bonds. D) Water will act as a hydrogen bond acceptor with hydroxyl groups. E) A network of electrostatic interactions exists between the molecules in water.

The hydrophobic effect is driven largely by the entropy of the non-polar substance.

Which of the following statements about water is false? A) Nonpolar substances decrease the entropy of water molecules. B) Water has a high melting point relative to its molecular mass. C) Water is a cohesive substance. D) The hydrophobic effect results when solutes are unable to break hydrogen bonds between water molecules. E) Water molecules make hydrogen bonds readily with each other and with other polar substances.

The hydrophobic effect results when solutes are unable to break hydrogen bonds between water molecules.

Which statement about the pK is not true? A) The pK is equal to the pH when [A-] = [HA]. B) The pK is equal to the pH at the maximum slope of the titration curve. C) The pK is equal to the pH at the midpoint of the titration. D) The pK is equal to the pH at the maximal buffering capacity.

The pK is equal to the pH at the maximum slope of the titration curve The pK is equal to the pH at the minimum slope of the titration curve

Consider the transfer of benzene from water to pure benzene. Which statement is false? A) T∆S is positive. B) Process is less favorable at higher temperature. C) The ∆G of transfer is negative. D) The ∆H of transfer is about zero.

The process is less favorable at a higher temperature

Consider a dialysis procedure in which an aqueous solution is separated from pure water by a membrane that is permeable to both water and solutes. Which statement is true? A) The random movement of molecules, called diffusion, proceeds only until the concentration is the same on each side of the dialysis membrane. B) Dialysis cannot separate molecules based upon their relative sizes. C) The tendency of solutes to diffuse from a region of high concentration to a region of lower concentration is thermodynamically favored. D) The membrane can be fine-tuned to selectively allow large molecules instead of smaller molecules to diffuse through it.

The tendency of solutes to diffuse from a region of high concentration to a region of lower concentration is thermodynamically favored

At the first horizontal inflection point in the titration curve of phosphoric acid, which statement is true? A) [H2PO4-] = [HPO42-] B) [H3PO4] = [H2PO4-] C) [H3PO4] > [H2PO4-] D) [H2PO4-] < [HPO42-]

[H3PO4] = [H2PO4-] The first horizontal inflection point indicates were pH = pK, thus where [H3PO4] = [H2PO4-]

The pK of ammonia is 9.25. Which statement is true at pH 7.0? A) Ammonia is an effective buffer at this pH. B) [NH4+] < [NH3] C) [NH4+] = [NH3] D) [NH4+] > [NH3]

[NH4+] > [NH3] When pK < pH, the acidic form predominates