Chapter 2 Quizzes

Regarding the Henderson-Hasselbalch equation, all of the following statements are true except: Question options: A) the Henderson-Hasselbalch equation is most useful for determining the molar amount of strong acid in solution. B) the Henderson-Hassebalch equation relates the pH to the pKa and the log of the ratio of dissociated to undissociated acid. C) the Henderson-Hasselbalch equation can be used to calculate the pKa for a weak acid, if the pH and the ratio of base to acid can be determined. D) the Henderson-Hasselbalch equation is useful for calculating the molar ratio of base to acid to achieve a given pH. E) the Henderson-Hasselbalch equation is derived from the formula for the dissociation constant of a weak acid, expressing it in logarithmic form.

A

The native three-dimensional structure of a macromolecule is not maintained primarily by: Question options: A) covalent bonds. B) ionic interactions. C) hydrogen bonds. D) hydrophobic interactions.

A

Which of the following is true about condensation reactions? Question options: A) Condensation reactions involve the loss of the elements of water. B) A typical condensation reaction is the formation of ADP from ATP and inorganic phosphate. C) Condensation reactions involve the depolymerizion of macromolecules. D) Condensation reactions are invariably exergonic.

A

Which of the following is true of hydrogen bonds? Question options: A) The attraction between the oxygen atom of a water molecule and the hydrogen atom of another water molecule constitutes a hydrogen bond. B) Hydrogen bonds form as covalent bonds between positively and negatively charged ions. C) Hydrogen bonds form between nonpolar portions of biomolecules. D) All of the above are true.

A

Which of the following statements about buffers is true? Question options: A) Buffers work best when the pH of the solution is within 1 pH unit of its pKa. B) They usually consist of a strong acid and its conjugate base. C) Although some problems may arise, the body could survive without buffers. D) Their effectiveness does not depend upon their concentration.

A

A true statement about hydrophobic interactions is that they: Question options: A) have bonding energies of approximately 20-40 Kjoule per mole. B) do not contribute to the structure of water-soluble proteins. C) are the driving force in the formation of micelles of amphipathic compounds in water. D) primarily involve the effect of polar solutes on the entropy of aqueous systems. E) involve the ability of water to denature proteins.

C

Amphiphilic substances: Question options: A) are hydrocarbons. B) do not aggregate. C) have one end that will dissolve in water and one end that will dissolve in a nonpolar environment. D) none of the above.

C

Hydrophobic interactions account for: Question options: A) the tendency of lipids to disperse in water. B) why the polar regions of molecules are associated with water. C) why the nonpolar regions of molecules cluster together in water. D) why biomolecules are amphipathic.

C

Which of the following is true for the polymerization reactions that produce proteins, polysaccharides and nucleic acids? Question options: A) They all form energy-rich molecules. B) They all produce a new carbon-carbon bond. C) They involve bond formation by the elimination of water. D) They produce symmetrical molecules. E) They form only repeated units.

C

A conjugate acid-base pair consists of two substances related by the donating and accepting of a proton. Question options: True False

T

The Henderson-Hasselbach equation relates the pH of a solution to the pKa and the concentration of acid and salt. Question options: True False

T

Water molecules dissociate producing hydrogen ions (H+), and hydroxide ions (OH-). Regarding the ion product of water, all of the following statements are true except: Question options: A) Because the extent of dissociation is very small, the concentration of pure water remains essentially at 55.5 M. B) In an aqueous solution the concentrations of hydrogen ions and hydroxide ions are inversely proportional. C) At equilibrium, the product of the concentration of the dissociated ions divided by the concentration of the undissociated water is a constant, K. D) Kw is a constant representing the ion product of water and is equivalent to 1 x 10-14. E) If H+ is added to an aqueous solution, OH- increases proportionately.

E

Which of the following would make the best buffer at pH 10.0? Question options: A) Histidine (pKa = 6.0) B) Na2HPO4/Na3PO4 (pKa = 12.4) C) tris-Hydroxymethyl aminomethane (pKa = 8.1) D) Acetic acid and sodium acetate (pKa = 4.8) E) Methylammonium chloride and methylamine (pKa = 10.6)

E

A pH change from 6.0 to 8.0 reflects an increase in the proton concentration ([H+]) by a factor of 100. Question options: True False

F

Strong acids can serve as buffers but weak acids cannot. Question options: True False

F

Many of the properties of water can be accounted for by the fact that: Question options: A) it is polar. B) it forms hydrogen bonds. C) it is bent. D) all of the above.

D

Which of the following is true about hydrogen bonds? Question options: A) Hydrogen bonds are longer and stronger than covalent bonds. B) The geometry of a water molecule results in the equal sharing of electrons between the hydrogen and oxygen. C) Hydrogen bonds must involve at least one water molecule. D) Polar molecules are soluble in water because they can form hydrogen bonds with water molecules.

D

Which substance would be a suitable buffer at pH 7.6? Question options: A) one with a pKa of 3.8 B) one with a pKa of 4.8 C) one with a pKa of 6.5 D) one with a pKa of 8.0 E) none of the above

D

If equal amounts of HPO4 2- and PO4 3- are mixed in water, estimate the resulting pH. The pKas of the phosphoric acid are 2.1, 7.2, and 12.4. Question options: A) 12.4 B) 7.2 C) 9.5 D) 2.1 E) 4.5

???

A polar bond is one in which there is: Question options: A) equal sharing of electrons. B) unequal sharing of electrons. C) a hydrogen atom. D) bonding between two atoms of the same element.

B

The three-dimensional structure of macromolecules is formed and maintained primarily through noncovalent interactions. Which one of the following is not considered a noncovalent interaction? Question options: A) hydrophobic interactions B) carbon-carbon bonds C) ionic interactions D) van der Waals interactions E) hydrogen bonds

B