Question 1

Which of the following is important to know when deciding if a given buffer will be effective for an experiment?

Accepted Answer

A)  the pKa of the buffer compound 
B)  the buffer capacity 
C)  the concentration of the buffer 
D)  whether the experiment is likely to generate hydrogen ions or hydroxide ions 
E)  all of these are important considerations 
A)  the pKa of the buffer compound 
B)  the buffer capacity 
C)  the concentration of the buffer 
D)  whether the experiment is likely to generate hydrogen ions or hydroxide ions 
E)  all of these are important considerations

Question 2

The water molecule is polar because:

Accepted Answer

A)  Electrons are not distributed symmetrically in the molecule. 
B)  The hydrogen atoms are found on one "side" of the molecule. 
C)  Hydrogen is less electronegative than oxygen. 
D)  The hydrogen atoms are found on one "side" of the molecule and hydrogen is less electronegative than oxygen. 
E)  All of these are correct. 
A)  Electrons are not distributed symmetrically in the molecule. 
B)  The hydrogen atoms are found on one "side" of the molecule. 
C)  Hydrogen is less electronegative than oxygen. 
D)  The hydrogen atoms are found on one "side" of the molecule and hydrogen is less electronegative than oxygen. 
E)  All of these are correct.

Question 3

In a titration of a weak acid by a strong base

Accepted Answer

A)  two equivalents of base are always needed to neutralize all the acid present 
B)  the equivalence point cannot be defined exactly 
C)  there is a region in which the pH changes slowly 
D)  the equivalence point depends on the nature of the added base 
A)  two equivalents of base are always needed to neutralize all the acid present 
B)  the equivalence point cannot be defined exactly 
C)  there is a region in which the pH changes slowly 
D)  the equivalence point depends on the nature of the added base

Question 4

The ion product constant for water (Kw) is equal to:

Accepted Answer

A)  1014 
B)  107 
C)  100 
D)  10−7 
E)  10−14 
A)  1014 
B)  107 
C)  100 
D)  10−7 
E)  10−14

Question 5

When does a weak acid buffer best?

Accepted Answer

A)  From one pH unit below its pKa to its pKa. 
B)  From its pKa to one pH unit above its pKa. 
C)  Within one pH unit of its pKa, both above and below. 
D)  Weak acids do not make good buffers at all. 
A)  From one pH unit below its pKa to its pKa. 
B)  From its pKa to one pH unit above its pKa. 
C)  Within one pH unit of its pKa, both above and below. 
D)  Weak acids do not make good buffers at all.

Question 6

Exhibit 2B
Contains information on the pK's of some common buffers.
$\begin{array}{llrc}
\text { Buffer } & \mathbf{p K} 1 & \mathbf{p K 2} & \mathbf{p K} 3 \
\hline \text { Acetate } & 4.75 & & \
\text { Ammonia } & 9.25 & & \
\text { Carbonic acid } & 6.37 & 10.20 & \
\text { Citric acid } & 3.09 & 4.75 & 5.41 \
\text { Formic Acid } & 3.75 & & \
\text { Phosphoric acid } & 2.14 & 7.20 & 12.4 \
\text { Pyruvic acid } & 2.50 & & \
\text { Tris } & 8.3 & &
\end{array}$

-Refer to Exhibit 2B. Which of the following would make the best buffer at pH =10.0?

Accepted Answer

A)  Acetic acid and sodium acetate 
B)  Tris and its acid form 
C)  H2CO3 and NaHCO3 
D)  Na2HPO4 and NaH2PO4 
E)  NaHCO3 and Na2CO3 
A)  Acetic acid and sodium acetate 
B)  Tris and its acid form 
C)  H2CO3 and NaHCO3 
D)  Na2HPO4 and NaH2PO4 
E)  NaHCO3 and Na2CO3

Question 7

Exhibit 2A The structure of ATP with various groups labeled.Group III is the entire phosphate group.
  
-Refer to Exhibit 2A. Which of the groups could not act as a proton acceptor in a hydrogen bond?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
E)  All can accept a hydrogen in a hydrogen bond. 
A)  I 
B)  II 
C)  III 
D)  IV 
E)  All can accept a hydrogen in a hydrogen bond.

Question 8

Exhibit 2B
Contains information on the pK's of some common buffers.
$\begin{array}{llrc}
\text { Buffer } & \mathbf{p K} 1 & \mathbf{p K 2} & \mathbf{p K} 3 \
\hline \text { Acetate } & 4.75 & & \
\text { Ammonia } & 9.25 & & \
\text { Carbonic acid } & 6.37 & 10.20 & \
\text { Citric acid } & 3.09 & 4.75 & 5.41 \
\text { Formic Acid } & 3.75 & & \
\text { Phosphoric acid } & 2.14 & 7.20 & 12.4 \
\text { Pyruvic acid } & 2.50 & & \
\text { Tris } & 8.3 & &
\end{array}$

-Refer to Exhibit 2B. An ammonium buffer would work well at this pH:

Accepted Answer

A)  5.6 
B)  7.0 
C)  9.0 
D)  11.0 
E)  None of these 
A)  5.6 
B)  7.0 
C)  9.0 
D)  11.0 
E)  None of these

Question 9

Exhibit 2B
Contains information on the pK's of some common buffers.
$\begin{array}{llrc}
\text { Buffer } & \mathbf{p K} 1 & \mathbf{p K 2} & \mathbf{p K} 3 \
\hline \text { Acetate } & 4.75 & & \
\text { Ammonia } & 9.25 & & \
\text { Carbonic acid } & 6.37 & 10.20 & \
\text { Citric acid } & 3.09 & 4.75 & 5.41 \
\text { Formic Acid } & 3.75 & & \
\text { Phosphoric acid } & 2.14 & 7.20 & 12.4 \
\text { Pyruvic acid } & 2.50 & & \
\text { Tris } & 8.3 & &
\end{array}$

-Refer to Exhibit 2B. A carbonate buffer would work well at this pH:

Accepted Answer

A)  4.0 
B)  6.0 
C)  8.0 
D)  10.0 
E)  6.0 and 10.0 
A)  4.0 
B)  6.0 
C)  8.0 
D)  10.0 
E)  6.0 and 10.0

Question 10

Which of the following classes of compounds is hydrophilic?

Accepted Answer

A)  Sugars 
B)  Fatty acids 
C)  Amino acids 
D)  Sugars and amino acids. 
E)  All of these 
A)  Sugars 
B)  Fatty acids 
C)  Amino acids 
D)  Sugars and amino acids. 
E)  All of these

Question 11

What is the pH of an acetic acid solution where the concentration of acetic acid is 2 mM and the concentration of sodium acetate is 20 mM. The pKa of acetic acid is 4.76.

Accepted Answer

A)  5.76 
B)  10.6 
C)  12.6 
D)  8.8 
A)  5.76 
B)  10.6 
C)  12.6 
D)  8.8

Question 12

Which of the following elements has the highest electronegativity?

Accepted Answer

A)  C 
B)  H 
C)  N 
D)  O 
E)  P 
A)  C 
B)  H 
C)  N 
D)  O 
E)  P

Question 13

The substance most likely to form a micelle is

Accepted Answer

A)  acetic acid 
B)  sodium palmitate 
C)  methyl alcohol 
D)  acetone 
A)  acetic acid 
B)  sodium palmitate 
C)  methyl alcohol 
D)  acetone

Question 14

If a solution has a pH = 9.6, the [H+] is

Accepted Answer

A)  2.5 × 1010 
B)  9.6 M 
C)  2.5 M 
D)  2.5 × 10−10 M 
E)  9.6 × 10−10 M 
A)  2.5 × 1010 
B)  9.6 M 
C)  2.5 M 
D)  2.5 × 10−10 M 
E)  9.6 × 10−10 M

Question 15

Which of the following molecules is polar?

Accepted Answer

A)  CCl4 
B)  CH4 
C)  CO2 
D)  NH3 
E)  None of these molecules is polar. 
A)  CCl4 
B)  CH4 
C)  CO2 
D)  NH3 
E)  None of these molecules is polar.

Question 16

Hydrogen bonds can only form when the hydrogen atom is involved in a polar bond.

Accepted Answer

A) True 
 B)False

Question 17

The dissociation constant for an acid is 1 × 10−6. What is its pKa?

Accepted Answer

A)  −6 
B)  6 
C)  0.6 
D)  −0.6 
A)  −6 
B)  6 
C)  0.6 
D)  −0.6

Question 18

The pH of a solution of 0.04 M HCl is:

Accepted Answer

A)  4 
B)  1.4 
C)  0.4 
D)  0.04 
E)  The pH cannot be determined 
A)  4 
B)  1.4 
C)  0.4 
D)  0.04 
E)  The pH cannot be determined

Question 19

Which of the following is a true statement?

Accepted Answer

A)  most substances contract when they freeze. 
B)  water expands when it freezes. 
C)  hydrogen bonding is related to water's tendency to expand as it freezes. 
D)  all of these are true 
A)  most substances contract when they freeze. 
B)  water expands when it freezes. 
C)  hydrogen bonding is related to water's tendency to expand as it freezes. 
D)  all of these are true

Question 20

Which of the following characteristics makes for a good hydrogen bond donor?

Accepted Answer

A)  a high electronegativity 
B)  a nonbonding pair of electrons 
C)  both of the above 
D)  neither of the above 
A)  a high electronegativity 
B)  a nonbonding pair of electrons 
C)  both of the above 
D)  neither of the above

Exam 2: Water: the Solvent for Biochemical Reactions

Which of the following is important to know when deciding if a given buffer will be effective for an experiment?

The water molecule is polar because:

In a titration of a weak acid by a strong base

The ion product constant for water (Kw) is equal to:

When does a weak acid buffer best?

Exhibit 2A The structure of ATP with various groups labeled.Group III is the entire phosphate group. -Refer to Exhibit 2A. Which of the groups could not act as a proton acceptor in a hydrogen bond?

Which of the following classes of compounds is hydrophilic?

What is the pH of an acetic acid solution where the concentration of acetic acid is 2 mM and the concentration of sodium acetate is 20 mM. The pKa of acetic acid is 4.76.

Which of the following elements has the highest electronegativity?

The substance most likely to form a micelle is

If a solution has a pH = 9.6, the [H+] is

Which of the following molecules is polar?

Hydrogen bonds can only form when the hydrogen atom is involved in a polar bond.

The dissociation constant for an acid is 1 × 10−6. What is its pKa?

The pH of a solution of 0.04 M HCl is:

Which of the following is a true statement?

Which of the following characteristics makes for a good hydrogen bond donor?

Biochemistry and the Organization of Cells

Amino Acids and Peptides

The Three-Dimensional Structure of Proteins

Protein Purification and Characterization Techniques

The Behavior of Proteins: Enzymes

The Behavior of Proteins: Enzymes, Mechanisms, and Control

Lipids and Proteins Are Associated in Biological Membranes

Nucleic Acids: How Structure Conveys Information

Biosynthesis of Nucleic Acids: Replication

Transcription of the Genetic Code: Biosynthesis of RNA

Protein Synthesis: Translation of the Genetic Message

Nucleic Acid Biotechnology Techniques

Viruses, Cancer, and Immunology

The Importance of Energy Changes and Electron Transfer in Metabolism

Carbohydrates

Glycolysis

Storage Mechanisms and Control in Carbohydrate Metabolism

The Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Lipid Metabolism

Photosynthesis

The Metabolism of Nitrogen

Integration of Metabolism: Cellular Signaling

Filters

The ion product constant for water (K_w) is equal to:

What is the pH of an acetic acid solution where the concentration of acetic acid is 2 mM and the concentration of sodium acetate is 20 mM. The pK_a of acetic acid is 4.76.

If a solution has a pH = 9.6, the [H⁺] is

The dissociation constant for an acid is 1 × 10−⁶. What is its pK_a?