Question 1

Which of the following statements about water is not true?

Accepted Answer

A) The electron-rich oxygen atom of one water molecule can interact with the electron-poor proton on another water molecule to form a hydrogen bond. 
B) Liquid water is only 15% less hydrogen bonded than ice. 
C) Water is a nonpolar molecule that with a bent molecular geometry. 
D) Water can form highly ordered,cage-like,structures around nonpolar molecules. 
E) Water is a key player in the energetics of hydrophobic interactions. 
A) The electron-rich oxygen atom of one water molecule can interact with the electron-poor proton on another water molecule to form a hydrogen bond. 
B) Liquid water is only 15% less hydrogen bonded than ice. 
C) Water is a nonpolar molecule that with a bent molecular geometry. 
D) Water can form highly ordered,cage-like,structures around nonpolar molecules. 
E) Water is a key player in the energetics of hydrophobic interactions.

Question 2

Covalent C─C and C─H bonds have bond strengths that are approximately ____ times higher than those of H-bonds.

Accepted Answer

A) 2 
B) 5 
C) 10 
D) 20 
E) 100 
A) 2 
B) 5 
C) 10 
D) 20 
E) 100

Question 3

Which of the following is the best explanation for the hydrophobic effect?

Accepted Answer

A) It is caused by an affinity of hydrophobic groups for each other. 
B) It is caused by the affinity of water for hydrophobic groups. 
C) It is an entropic effect,caused by the desire of water molecules to increase their entropy by forming highly ordered structures around the hydrophobic groups. 
D) It is an entropic effect,caused by the desire of water molecules to increase their entropy by excluding hydrophobic groups,which they must otherwise surround with highly ordered structures. 
E) It is an entropic effect caused by the desire of hydrophobic groups to increase their entropy by associating with other hydrophobic groups. 
A) It is caused by an affinity of hydrophobic groups for each other. 
B) It is caused by the affinity of water for hydrophobic groups. 
C) It is an entropic effect,caused by the desire of water molecules to increase their entropy by forming highly ordered structures around the hydrophobic groups. 
D) It is an entropic effect,caused by the desire of water molecules to increase their entropy by excluding hydrophobic groups,which they must otherwise surround with highly ordered structures. 
E) It is an entropic effect caused by the desire of hydrophobic groups to increase their entropy by associating with other hydrophobic groups.

Question 4

Matching

-For the ______ represented by D-H$\dots$A,the donor D is weakly acidic and the acceptor A is weakly basic.

Accepted Answer

A)  hydrogen bond 
B)  rotational 
C)  H3PO4 
D)  H2PO4– 
E)  HPO4 2–
F) disordered 
G) positive entropy 
H) negative entropy  
I) higher electronegativity 
J) insoluble
K) tetrahedral arrangement 
L) acid
M) base
N) only partially ionized 
A)  hydrogen bond 
B)  rotational 
C)  H3PO4 
D)  H2PO4– 
E)  HPO4 2–
F) disordered 
G) positive entropy 
H) negative entropy  
I) higher electronegativity 
J) insoluble
K) tetrahedral arrangement 
L) acid
M) base
N) only partially ionized

Question 5

The capacity of a buffer to resist changes in pH upon addition of protons or hydroxide ions depends on

Accepted Answer

A) the pKa of the weak acid in the buffer. 
B) the pH of the buffer. 
C) the total concentration of the weak acid and its conjugate base in the buffer. 
D) all of the above 
E) none of the above 
A) the pKa of the weak acid in the buffer. 
B) the pH of the buffer. 
C) the total concentration of the weak acid and its conjugate base in the buffer. 
D) all of the above 
E) none of the above

Question 6

Weak acids

Accepted Answer

A) are only partially ionized in an aqueous solution. 
B) give solutions with a high pH. 
C) do not provide hydronium ions. 
D) are almost insoluble in water. 
E) are of no value in a buffering system. 
A) are only partially ionized in an aqueous solution. 
B) give solutions with a high pH. 
C) do not provide hydronium ions. 
D) are almost insoluble in water. 
E) are of no value in a buffering system.

Question 7

The strongest noncovalent interactions are

Accepted Answer

A) ionic interactions. 
B) hydrogen bonds. 
C) dipole-dipole interactions. 
D) London dispersion forces. 
E) van der Waals forces. 
A) ionic interactions. 
B) hydrogen bonds. 
C) dipole-dipole interactions. 
D) London dispersion forces. 
E) van der Waals forces.

Question 8

In a hydrogen bond between a water molecule and another biomolecule

Accepted Answer

A) a hydrogen ion on the water molecule forms an ionic bond with a hydride ion on the other molecule. 
B) the partial charge on a hydrogen of the water molecule interacts with the partial charge on a hydrogen of the other molecule. 
C) the hydrogen bond will typically form between a hydrogen atom of the water molecule and either a nitrogen,sulfur,or oxygen atom of the other molecule. 
D) a hydrogen on the water molecule forms a covalent bond with a hydrogen atom on the other molecule. 
E) the hydrogen atom is located between an oxygen atom of the water and a carbon atom of the other molecule. 
A) a hydrogen ion on the water molecule forms an ionic bond with a hydride ion on the other molecule. 
B) the partial charge on a hydrogen of the water molecule interacts with the partial charge on a hydrogen of the other molecule. 
C) the hydrogen bond will typically form between a hydrogen atom of the water molecule and either a nitrogen,sulfur,or oxygen atom of the other molecule. 
D) a hydrogen on the water molecule forms a covalent bond with a hydrogen atom on the other molecule. 
E) the hydrogen atom is located between an oxygen atom of the water and a carbon atom of the other molecule.

Question 9

A buffer contains 0.010 mol of lactic acid (pKa = 3.86)and 0.050 mol sodium lactate per liter of aqueous solution.
a.Calculate the pH of this buffer.
b.Calculate the pH after 5.0 mL of 0.50 M HCl is added to 1 liter of the buffer (assume the total volume will be 1005 mL).

Accepted Answer

a.pH = pK_a + log [A⁻

Question 10

Hydrogen bonds within liquid water

Accepted Answer

A) are attractions between protons and oxygen nuclei. 
B) are attractions between two hydrogen atoms. 
C) are attractions between protons and hydroxide ions. 
D) are ion-induced dipole attractions. 
E) are dipole-dipole attractions. 
A) are attractions between protons and oxygen nuclei. 
B) are attractions between two hydrogen atoms. 
C) are attractions between protons and hydroxide ions. 
D) are ion-induced dipole attractions. 
E) are dipole-dipole attractions.

Question 11

A graduate student at SDSU wants to measure the activity of a particular enzyme at pH 4.0.To buffer her reaction,she will use a buffer system based on one of the acids listed below,which acid is most appropriate for the experiment?

Accepted Answer

A) Formic acid (Ka 1.78 × 10−4) 
B) MES (Ka 8.13 × 10−7) 
C) PIPES (Ka 1.74 × 10−7) 
D) Tris (Ka 8.32 × 10−9) 
E) Piperidine (Ka 7.58 × 10−12) 
A) Formic acid (Ka 1.78 × 10−4) 
B) MES (Ka 8.13 × 10−7) 
C) PIPES (Ka 1.74 × 10−7) 
D) Tris (Ka 8.32 × 10−9) 
E) Piperidine (Ka 7.58 × 10−12)

Question 12

The pKs of succinic acid are 4.21 and 5.64.How many grams of monosodium succinate (FW = 140 g/mol)and disodium succinate (FW = 162 g/mol)must be added to 1 L of water to produce a solution with a pH 5.28 and a total solute concentration of 100 mM? (Assume the total volume remains 1 liter,answer in grams monosodium succinate,grams disodium succinate,respectively. )

Accepted Answer

A) 11.3 g,4.2 g 
B) 9)7 g,4.9 g 
C) 4)9 g,9.7 g 
D) 14.9 g,1.1 g 
E) 1)1 g,14.9 g 
A) 11.3 g,4.2 g 
B) 9)7 g,4.9 g 
C) 4)9 g,9.7 g 
D) 14.9 g,1.1 g 
E) 1)1 g,14.9 g

Question 13

To make a phosphate buffer at pH 6.82 starting with one liter of 10 mM phosphoric acid (pKs are 2.15,6.82,and 12.38),you could add

Accepted Answer

A) 5 millimoles of HCl. 
B) 20 millimoles of K+. 
C) 25 millimoles of HCl. 
D) 15 millimoles of KOH. 
E) You can't make a buffer by adding HCl or KOH. 
A) 5 millimoles of HCl. 
B) 20 millimoles of K+. 
C) 25 millimoles of HCl. 
D) 15 millimoles of KOH. 
E) You can't make a buffer by adding HCl or KOH.

Question 14

Molecules such as methanol and ethanol are very soluble in water because

Accepted Answer

A) they tend to avoid contact with each other. 
B) they contain C─H groups that donate H-bonds to water. 
C) they contain C─H groups that accept H-bonds from water 
D) they contain O─H groups that can form multiple H-bonds with water. 
E) they do not form intermolecular H-bonds 
A) they tend to avoid contact with each other. 
B) they contain C─H groups that donate H-bonds to water. 
C) they contain C─H groups that accept H-bonds from water 
D) they contain O─H groups that can form multiple H-bonds with water. 
E) they do not form intermolecular H-bonds

Question 15

Methanol can act both as a H-bond donor and as a H-bond acceptor.What is the maximal number of H-bonds a single molecule of methanol can form with surrounding water molecules.

Accepted Answer

A) 1 
B) 2 
C) 3 
D) 4 
E) 5 
A) 1 
B) 2 
C) 3 
D) 4 
E) 5

Question 16

Solutions that contain a mixture of a weak acid and its conjugate base are known to resist changes in pH.
a.Calculate the pH of 1.0 L of an aqueous solution containing 75 mmol of MES (pKa = 6.09)and 25 mmol of its conjugate base.
b.How much of a 5.0 M NaOH solution do you need to add to raise the pH to 6.09?

Accepted Answer

a.pH = pK_a + log [A⁻

Question 17

Matching

-The 104.5° bond angle in the water molecule is the result of the ______ of electron orbitals around oxygen.

Accepted Answer

A)  hydrogen bond 
B)  rotational 
C)  H3PO4 
D)  H2PO4– 
E)  HPO4 2–
F) disordered 
G) positive entropy 
H) negative entropy  
I) higher electronegativity 
J) insoluble
K) tetrahedral arrangement 
L) acid
M) base
N) only partially ionized 
A)  hydrogen bond 
B)  rotational 
C)  H3PO4 
D)  H2PO4– 
E)  HPO4 2–
F) disordered 
G) positive entropy 
H) negative entropy  
I) higher electronegativity 
J) insoluble
K) tetrahedral arrangement 
L) acid
M) base
N) only partially ionized

Question 18

Amphiphilic molecules

Accepted Answer

A) have both oxidizing and reducing groups. 
B) are micelles. 
C) have chromophores in two different wavelength regions. 
D) have both acidic and basic groups. 
E) have both hydrophilic and hydrophobic groups. 
A) have both oxidizing and reducing groups. 
B) are micelles. 
C) have chromophores in two different wavelength regions. 
D) have both acidic and basic groups. 
E) have both hydrophilic and hydrophobic groups.

Question 19

The pH of coffee is 5.6.The pH of grapefruit juice is 2.6.This means that the proton concentration in coffee is

Accepted Answer

A) a thousand times higher than in grapefruit juice. 
B) a thousand times lower than in grapefruit juice. 
C) 3000 times lower than in grapefruit juice. 
D) 3 times the proton concentration of grapefruit juice. 
E) 3000 times higher than in grapefruit juice. 
A) a thousand times higher than in grapefruit juice. 
B) a thousand times lower than in grapefruit juice. 
C) 3000 times lower than in grapefruit juice. 
D) 3 times the proton concentration of grapefruit juice. 
E) 3000 times higher than in grapefruit juice.

Question 20

Which of the following statements about water is incorrect?

Accepted Answer

A) It is a small,polar molecule with a low dielectric constant. 
B) It has a marked dipole moment. 
C) It is largely hydrogen bonded,although any single H-bond exists only for a very short period of time (~10-12 s ). 
D) Acid-base reactions are very fast due to the mobility of hydronium ions in water which is a consequence of the ability of individual protons to "jump" from one water molecule to another. 
E) It has a bent geometry with each O─H bond approximately 0.958 Å long and with an O─H bond energy of approximately 460 kJ/mol. 
A) It is a small,polar molecule with a low dielectric constant. 
B) It has a marked dipole moment. 
C) It is largely hydrogen bonded,although any single H-bond exists only for a very short period of time (~10-12 s ). 
D) Acid-base reactions are very fast due to the mobility of hydronium ions in water which is a consequence of the ability of individual protons to "jump" from one water molecule to another. 
E) It has a bent geometry with each O─H bond approximately 0.958 Å long and with an O─H bond energy of approximately 460 kJ/mol.

Exam 2: Water

Which of the following statements about water is not true?

Covalent C─C and C─H bonds have bond strengths that are approximately ____ times higher than those of H-bonds.

Which of the following is the best explanation for the hydrophobic effect?

Matching -For the ______ represented by D-H …\dots… A,the donor D is weakly acidic and the acceptor A is weakly basic.

The capacity of a buffer to resist changes in pH upon addition of protons or hydroxide ions depends on

Weak acids

The strongest noncovalent interactions are

In a hydrogen bond between a water molecule and another biomolecule

A buffer contains 0.010 mol of lactic acid (pKa = 3.86)and 0.050 mol sodium lactate per liter of aqueous solution. a.Calculate the pH of this buffer. b.Calculate the pH after 5.0 mL of 0.50 M HCl is added to 1 liter of the buffer (assume the total volume will be 1005 mL).

Hydrogen bonds within liquid water

A graduate student at SDSU wants to measure the activity of a particular enzyme at pH 4.0.To buffer her reaction,she will use a buffer system based on one of the acids listed below,which acid is most appropriate for the experiment?

To make a phosphate buffer at pH 6.82 starting with one liter of 10 mM phosphoric acid (pKs are 2.15,6.82,and 12.38),you could add

Molecules such as methanol and ethanol are very soluble in water because

Methanol can act both as a H-bond donor and as a H-bond acceptor.What is the maximal number of H-bonds a single molecule of methanol can form with surrounding water molecules.

Matching -The 104.5° bond angle in the water molecule is the result of the ______ of electron orbitals around oxygen.

Amphiphilic molecules

The pH of coffee is 5.6.The pH of grapefruit juice is 2.6.This means that the proton concentration in coffee is

Which of the following statements about water is incorrect?

Introduction to the Chemistry of Life

Nucleotides, nucleic Acids, and Genetic Information

Amino Acids

Proteins: Primary Structure

Proteins: Three-Dimensional Structure

Protein Function Part I: Myoglobin and Hemoglobin

Carbohydrates

Lipids and Biological Membranes

Membrane Transport

Enzyme Catalysis

Enzyme Kinetics, inhibition and Control

Biochemical Signaling

Introduction to Metabolism

Glucose Catabolism

Glycogen Metabolism and Gluconeogenesis

Citric Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Mammalian Fuel Metabolism: Integration and Regulation

Nucleotide Metabolism

Nucleic Acid Structure

DNA Replication, repair and Recombination

Transcription and Rna Processing

Protein Synthesis

Regulation of Gene Expression

Filters

Matching -For the ______ represented by D-H $\dots$ A,the donor D is weakly acidic and the acceptor A is weakly basic.

A buffer contains 0.010 mol of lactic acid (pK_a = 3.86)and 0.050 mol sodium lactate per liter of aqueous solution. a.Calculate the pH of this buffer. b.Calculate the pH after 5.0 mL of 0.50 M HCl is added to 1 liter of the buffer (assume the total volume will be 1005 mL).