Question 1

For each of the pairs below,circle the conjugate base.

Accepted Answer

The answer of For each of the pairs below,circle the...

Question 2

Which of these statements about hydrogen bonds is not true?

Accepted Answer

A) Hydrogen bonds account for the anomalously high boiling point of water. 
B) In liquid water,the average water molecule forms hydrogen bonds with three to four other water molecules. 
C) Individual hydrogen bonds are much weaker than covalent bonds. 
D) Individual hydrogen bonds in liquid water exist for many seconds and sometimes for minutes. 
E) The strength of a hydrogen bond depends on the linearity of the three atoms involved in the bond. 
A) Hydrogen bonds account for the anomalously high boiling point of water. 
B) In liquid water,the average water molecule forms hydrogen bonds with three to four other water molecules. 
C) Individual hydrogen bonds are much weaker than covalent bonds. 
D) Individual hydrogen bonds in liquid water exist for many seconds and sometimes for minutes. 
E) The strength of a hydrogen bond depends on the linearity of the three atoms involved in the bond.

Question 3

Phosphoric acid is tribasic,with pKa's of 2.14,6.86,and 12.4.The ionic form that predominates at pH 3.2 is:

Accepted Answer

A) H3PO4. 
B) H2PO4-. 
C) HPO42-. 
D) PO43-. 
E) none of the above. 
A) H3PO4. 
B) H2PO4-. 
C) HPO42-. 
D) PO43-. 
E) none of the above.

Question 4

A compound has a pKa of 7.4.To 100 mL of a 1.0 M solution of this compound at pH 8.0 is added 30 mL of 1.0 M hydrochloric acid.The resulting solution is pH:

Accepted Answer

A) 6)5. 
B) 6)8. 
C) 7)2. 
D) 7)4. 
E) 7)5. 
A) 6)5. 
B) 6)8. 
C) 7)2. 
D) 7)4. 
E) 7)5.

Question 5

You want to maintain pH = 7.0 for an enzyme-catalyzed reaction that will produce hydrogen ions along with the desired product.At equal concentrations,which weak acid,if any,will serve as the better buffer for the reaction: Acid A,with pKa = 6.5 or Acid B,with pKa = 7.5?

Accepted Answer

A) Acid A 
B) Water is as good as either of the acids available. 
C) Acid B 
D) Both are equally effective. 
A) Acid A 
B) Water is as good as either of the acids available. 
C) Acid B 
D) Both are equally effective.

Question 6

Phosphoric acid (H3PO4)has three dissociable protons,with the pKa's shown below.Which form of phosphoric acid predominates in a solution at pH 4? Explain your answer.

Accepted Answer

At pH 4,the first dissociable proton (pK

Question 7

A true statement about hydrophobic interactions is that they:

Accepted Answer

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

Question 8

Define pKa for a weak acid in the following two ways: (1)in relation to its acid dissociation constant,Ka,and (2)by reference to a titration curve for the weak acid.

Accepted Answer

(1)pK_a = -log K_a. (2)pK_a is the value of pH

Question 9

The Henderson-Hasselbalch equation:

Accepted Answer

A) allows the graphic determination of the molecular weight of a weak acid from its pH alone. 
B) does not explain the behavior of di- or tri-basic weak acids. 
C) employs the same value for pKa for all weak acids. 
D) is equally useful with solutions of acetic acid and of hydrochloric acid. 
E) relates the pH of a solution to the pKa and the concentrations of acid and conjugate base. 
A) allows the graphic determination of the molecular weight of a weak acid from its pH alone. 
B) does not explain the behavior of di- or tri-basic weak acids. 
C) employs the same value for pKa for all weak acids. 
D) is equally useful with solutions of acetic acid and of hydrochloric acid. 
E) relates the pH of a solution to the pKa and the concentrations of acid and conjugate base.

Question 10

Three buffers are made by combining a 1 M solution of acetic acid with a 1 M solution of sodium acetate in the ratios shown below.
 
Which of these statements is true of the resulting buffers?

Accepted Answer

A) pH of buffer 1  pH of buffer 2 > pH of buffer 3 
D) The problem cannot be solved without knowing the value of pKa. 
E) None of the above 
A) pH of buffer 1  pH of buffer 2 > pH of buffer 3 
D) The problem cannot be solved without knowing the value of pKa. 
E) None of the above

Question 11

Explain the fact that triethylammonium chloride ((CH3CH2)3N•HCl)is more soluble in water than is triethylamine ((CH3CH2)3N).

Accepted Answer

The positive charge on the N atom in tri

Question 12

The aqueous solution with the highest pH is:

Accepted Answer

A) 1 M HCl. 
B) 1 M NH3 (pKa = 9.25). 
C) 0)5 M NaHCO3 (pKa = 3.77). 
D) 0)1 M NaOH. 
E) 0)001 M NaOH. 
A) 1 M HCl. 
B) 1 M NH3 (pKa = 9.25). 
C) 0)5 M NaHCO3 (pKa = 3.77). 
D) 0)1 M NaOH. 
E) 0)001 M NaOH.

Question 13

Consider an acetate buffer,initially at the same pH as its pKa (4.76).When sodium hydroxide (NaOH)is mixed with this buffer,the:

Accepted Answer

A) pH remains constant. 
B) pH rises more than if an equal amount of NaOH is added to an acetate buffer initially at pH 6.76. 
C) pH rises more than if an equal amount of NaOH is added to unbuffered water at pH 4.76. 
D) ratio of acetic acid to sodium acetate in the buffer falls. 
E) sodium acetate formed precipitates because it is less soluble than acetic acid. 
A) pH remains constant. 
B) pH rises more than if an equal amount of NaOH is added to an acetate buffer initially at pH 6.76. 
C) pH rises more than if an equal amount of NaOH is added to unbuffered water at pH 4.76. 
D) ratio of acetic acid to sodium acetate in the buffer falls. 
E) sodium acetate formed precipitates because it is less soluble than acetic acid.

Question 14

A 1.0 M solution of a compound with 2 ionizable groups (pKa's = 6.2 and 9.5;100 mL total)has a pH of 6.8.If a biochemist adds 60 mL of 1.0 M HCl to this solution,the solution will change to pH:

Accepted Answer

A) 5)60. 
B) 8)90. 
C) 9)13. 
D) 9)32. 
E) The pH cannot be determined from this information. 
A) 5)60. 
B) 8)90. 
C) 9)13. 
D) 9)32. 
E) The pH cannot be determined from this information.

Question 15

In which reaction below does water not participate as a reactant (rather than as a product)?

Accepted Answer

A) Conversion of an acid anhydride to two acids 
B) Conversion of an ester to an acid and an alcohol 
C) Conversion of ATP to ADP 
D) Photosynthesis 
E) Production of gaseous carbon dioxide from bicarbonate 
A) Conversion of an acid anhydride to two acids 
B) Conversion of an ester to an acid and an alcohol 
C) Conversion of ATP to ADP 
D) Photosynthesis 
E) Production of gaseous carbon dioxide from bicarbonate

Question 16

Dissolved solutes alter some physical (colligative)properties of the solvent water because they change the:

Accepted Answer

A) concentration of the water. 
B) hydrogen bonding of the water. 
C) ionic bonding of the water. 
D) pH of the water. 
E) temperature of the water. 
A) concentration of the water. 
B) hydrogen bonding of the water. 
C) ionic bonding of the water. 
D) pH of the water. 
E) temperature of the water.

Question 17

Name and briefly define five types of noncovalent interactions that occur between biological molecules.

Accepted Answer

(1)Hydrogen bonds: weak electrostatic at

Question 18

The pH of a solution of 0.1 M NaOH is:

Accepted Answer

A) 0)1. 
B) 1)0. 
C) 12.8. 
D) 13. 
E) 14. 
A) 0)1. 
B) 1)0. 
C) 12.8. 
D) 13. 
E) 14.

Question 19

A weak acid HA,has a pKa of 5.0.If 1.0 mol of this acid and 0.1 mol of NaOH were dissolved in one liter of water,what would the final pH be?

Accepted Answer

Combining 1 mol of weak acid w

Question 20

The pH of a solution of 1 M HCl is:

Accepted Answer

A) 0) 
B) 0)1. 
C) 1) 
D) 10. 
E) -1. 
A) 0) 
B) 0)1. 
C) 1) 
D) 10. 
E) -1.

Exam 2: Water

For each of the pairs below,circle the conjugate base.

Which of these statements about hydrogen bonds is not true?

Phosphoric acid is tribasic,with pKa's of 2.14,6.86,and 12.4.The ionic form that predominates at pH 3.2 is:

A compound has a pKa of 7.4.To 100 mL of a 1.0 M solution of this compound at pH 8.0 is added 30 mL of 1.0 M hydrochloric acid.The resulting solution is pH:

You want to maintain pH = 7.0 for an enzyme-catalyzed reaction that will produce hydrogen ions along with the desired product.At equal concentrations,which weak acid,if any,will serve as the better buffer for the reaction: Acid A,with pKa = 6.5 or Acid B,with pKa = 7.5?

Phosphoric acid (H3PO4)has three dissociable protons,with the pKa's shown below.Which form of phosphoric acid predominates in a solution at pH 4? Explain your answer.

A true statement about hydrophobic interactions is that they:

Define pKa for a weak acid in the following two ways: (1)in relation to its acid dissociation constant,Ka,and (2)by reference to a titration curve for the weak acid.

The Henderson-Hasselbalch equation:

Three buffers are made by combining a 1 M solution of acetic acid with a 1 M solution of sodium acetate in the ratios shown below. Which of these statements is true of the resulting buffers?

Explain the fact that triethylammonium chloride ((CH3CH2)3N•HCl)is more soluble in water than is triethylamine ((CH3CH2)3N).

The aqueous solution with the highest pH is:

Consider an acetate buffer,initially at the same pH as its pKa (4.76).When sodium hydroxide (NaOH)is mixed with this buffer,the:

A 1.0 M solution of a compound with 2 ionizable groups (pKa's = 6.2 and 9.5;100 mL total)has a pH of 6.8.If a biochemist adds 60 mL of 1.0 M HCl to this solution,the solution will change to pH:

In which reaction below does water not participate as a reactant (rather than as a product)?

Dissolved solutes alter some physical (colligative)properties of the solvent water because they change the:

Name and briefly define five types of noncovalent interactions that occur between biological molecules.

The pH of a solution of 0.1 M NaOH is:

A weak acid HA,has a pKa of 5.0.If 1.0 mol of this acid and 0.1 mol of NaOH were dissolved in one liter of water,what would the final pH be?

The pH of a solution of 1 M HCl is:

The Foundations of Biochemistry

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Phosphoric acid is tribasic,with pK_a's of 2.14,6.86,and 12.4.The ionic form that predominates at pH 3.2 is:

A compound has a pK_a of 7.4.To 100 mL of a 1.0 M solution of this compound at pH 8.0 is added 30 mL of 1.0 M hydrochloric acid.The resulting solution is pH:

Phosphoric acid (H₃PO₄)has three dissociable protons,with the pK_a's shown below.Which form of phosphoric acid predominates in a solution at pH 4? Explain your answer.

Define pK_a for a weak acid in the following two ways: (1)in relation to its acid dissociation constant,K_a,and (2)by reference to a titration curve for the weak acid.

Explain the fact that triethylammonium chloride ((CH₃CH₂)₃N•HCl)is more soluble in water than is triethylamine ((CH₃CH₂)₃N).

Consider an acetate buffer,initially at the same pH as its pK_a (4.76).When sodium hydroxide (NaOH)is mixed with this buffer,the:

A weak acid HA,has a pK_a of 5.0.If 1.0 mol of this acid and 0.1 mol of NaOH were dissolved in one liter of water,what would the final pH be?