Question 1

How do hydrogen bonds tend to affect the melting and boiling points of substances?

Accepted Answer

A)   They tend to increase both melting and boiling points.
B)   They tend to decrease both melting and boiling points.
C)   They tend to increase melting points and decrease boiling points.
D)   They tend to decrease melting points and increase boiling points.
E)   They do not have any affect on either melting or boiling points.F) C) and D)
G) A) and D)

Question 2

Which of the following acids would serve as a good buffer for a reaction at pH = 8.0?  Ka I.  acetic acid 1.76×10−5 II. H2PO4−6.31×10−8 III.  bicarbonate 5.6×10−11 IV.  TRIS 5.01×10−9\begin{array} { l l l } & \mathbf { K } _ { \mathbf { a } } \	ext { I. } & 	ext { acetic acid } & 1.76 	imes 10 - ^ { 5 } \	ext { II. } & \mathrm { H } _ { 2 } \mathrm { PO } _ { 4 } - & 6.31 	imes 10 ^ { - 8} \	ext { III. } & 	ext { bicarbonate } & 5.6 	imes 10 ^{- 11 }\	ext { IV. } & 	ext { TRIS } & 5.01 	imes 10 ^ { -  9}\end{array} I.  II.  III.  IV. ​Ka​ acetic acid H2​PO4​− bicarbonate  TRIS ​1.76×10−56.31×10−85.6×10−115.01×10−9​

Accepted Answer

A)   I
B)   II
C)   III
D)   IV E) A) and B)
F) None of the above

Question 3

Nonphysiological buffers such as HEPES and PIPES have come into common use because

Accepted Answer

A)   they are inexpensive
B)   they can be prepared much more easily than other buffers
C)   they have less tendency to interfere with reactions
D)   they contain nitrogenE) None of the above
F) A) and D) C

Question 4

Which substance would be the best buffer at pH 8 if it had to be able to buffer against either acid or base?

Accepted Answer

A)   one with a pKa of 7
B)   one with a pKa of 8
C)   one with a pKa of 9
D)   The pKa of a substance doesn't tell you whether it would be a good buffer at this pH.E) All of the above
F) B) and D)

Question 5

The dissociation constant for an acid with a pKa value of 6.0 is

Accepted Answer

A)   1 × 10−6
B)   −1 × 106
C)   1 × 106
D)   −1 × 10−6E) B) and C)
F) C) and D)

Question 6

Which of the following is true about ionic compounds?

Accepted Answer

A)   They are more likely to dissolve in non-polar solvents than covalent compounds.
B)   They always dissolve completely in water.
C)   They never dissolve in polar solvents.
D)   Some of them dissolve completely in water or other polar solvents, while others do not.E) A) and C)
F) C) and D)

Question 7

Hydrogen bonds

Accepted Answer

A)   play an important role in the solvent properties of water
B)   are not involved in protein structure
C)   play a role in the properties of DNA, but not of RNA
D)   give water a lower boiling point than expectedE) A) and D)
F) B) and C)

Question 8

For an acid that undergoes this reaction: HA ↔ H+ + A− Ka =

Accepted Answer

A)   [H+][A−]/[HA]
B)   [H+][HA]/[A−]
C)   [HA][A−]/[H+]
D)   [A−]/[HA][H+]
E)   [H+]/[HA][A−]F) B) and D)
G) All of the above

Question 9

Bases are

Accepted Answer

A)   proton donors.
B)   proton acceptors.
C)   hydrogen bond donors.
D)   hydrogen bond acceptors.E) None of the above
F) B) and C)

Question 10

What is the maximum number of hydrogen bonds a single water molecule can form?

Accepted Answer

A)   1
B)   2
C)   3
D)   4
E)   5F) B) and E)
G) A) and C)

Question 11

A hydrogen bond is a special type of

Accepted Answer

A)   dioole - dipole bond
B)   induced dipole - induced dipole bond
C)   covalent bond
D)   ionic bondE) All of the above
F) A) and D)

Question 12

A buffer solution

Accepted Answer

A)   is used to control the pH of a solution
B)   contains at least 100 times more of a weak acid than its conjugate base
C)   contains at least 100 times less of a weak acid than its conjugate base
D)   always has a pH of 7E) A) and B)
F) B) and D)

Question 13

Which of the following is true regarding hydrogen bonds.

Accepted Answer

A)   They can only form between two different molecules
B)   They are important in protein folding but not DNA structure
C)   They are important in DNA structure but not protein folding
D)   They can be found within a single moleculeE) A) and B)
F) A) and C) D

Question 14

Which of the following statements about hydrogen bonds is false?

Accepted Answer

A)   The donor is a hydrogen atom bonded to a less electronegative atom then hydrogen.
B)   The more linear the bond, the stronger the attraction.
C)   The acceptor must contain a non-bonded pair of electrons.
D)   It is a type of non-covalent bond.E) All of the above
F) A) and B)

Question 15

The ratio of a weak acid and its conjugate base at the point of maximum buffering capacity is

Accepted Answer

A)   1/1
B)   1/10
C)   10/1
D)   no definite ratio is neededE) C) and D)
F) None of the above

Question 16

Is water an acid or a base?

Accepted Answer

A)   Water is an acid.
B)   Water is a base.
C)   Water is both an acid and a base.
D)   Water is neither an acid nor a base.E) None of the above
F) A) and C)

Question 17

Which of the following is not true?

Accepted Answer

A)   A buffer is a solution which maintains a solution at a neutral pH
B)   Buffer solutions are made to resist change in pH
C)   Zwitterion buffers are less likely to interfere with biological reactions than non-zwitterions
D)   HEPES is a zwitterion bufferE) B) and C)
F) C) and D) A

Question 18

Which of the following molecules is amphipathic?

Accepted Answer

A)   sodium chloride
B)   acetic acid
C)   benzene
D)   palmitic acidE) None of the above
F) A) and C)

Question 19

Which of the following is true?

Accepted Answer

A)   The pH of a solution where the A− to HA ratio is 1 has a pH = pKa.
B)   If the pH does not equal the pKa, the solution is not a buffer.
C)   The best buffer for any experiment will always have a pH equal to the pKa.
D)   If a buffer has more weak acid than conjugate base, the pH will be higher than the pKa.E) A) and B)
F) A) and C)

Question 20

A micelle is a structure which

Accepted Answer

A)   aggregates with other micelles in water.
B)   has its polar groups on the outside and non-polar groups on the inside when in water.
C)   explains how soaps and detergents work.
D)   has its polar groups on the outside and non-polar groups on the inside when in water and explains how soaps and detergents work.
E)   All of these are true.F) A) and E)
G) A) and C)

Exam 2: Water: the Solvent for Biochemical Reactions

How do hydrogen bonds tend to affect the melting and boiling points of substances?

Correct Answer
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Correct Answer
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Nonphysiological buffers such as HEPES and PIPES have come into common use because

Correct Answer
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C

Which substance would be the best buffer at pH 8 if it had to be able to buffer against either acid or base?

Correct Answer
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The dissociation constant for an acid with a pK_a value of 6.0 is

Correct Answer
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Which of the following is true about ionic compounds?

Correct Answer
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Hydrogen bonds

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For an acid that undergoes this reaction: HA ↔ H⁺ + A− K_a =

Correct Answer
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Bases are

Correct Answer
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What is the maximum number of hydrogen bonds a single water molecule can form?

Correct Answer
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A hydrogen bond is a special type of

Correct Answer
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A buffer solution

Correct Answer
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Which of the following is true regarding hydrogen bonds.

Correct Answer
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D

Which of the following statements about hydrogen bonds is false?

Correct Answer
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The ratio of a weak acid and its conjugate base at the point of maximum buffering capacity is

Correct Answer
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Is water an acid or a base?

Correct Answer
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Which of the following is not true?

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A

Which of the following molecules is amphipathic?

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Which of the following is true?

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A micelle is a structure which

Correct Answer
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Exam 2: Water: the Solvent for Biochemical Reactions

How do hydrogen bonds tend to affect the melting and boiling points of substances?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Nonphysiological buffers such as HEPES and PIPES have come into common use because

Correct AnswerverifiedC

Which substance would be the best buffer at pH 8 if it had to be able to buffer against either acid or base?

Correct AnswerverifiedShow Answer

The dissociation constant for an acid with a pKa value of 6.0 is

Correct AnswerverifiedShow Answer

Which of the following is true about ionic compounds?

Correct AnswerverifiedShow Answer

Hydrogen bonds

Correct AnswerverifiedShow Answer

For an acid that undergoes this reaction: HA ↔ H+ + A− Ka =

Correct AnswerverifiedShow Answer

Bases are

Correct AnswerverifiedShow Answer

What is the maximum number of hydrogen bonds a single water molecule can form?

Correct AnswerverifiedShow Answer

A hydrogen bond is a special type of

Correct AnswerverifiedShow Answer

A buffer solution

Correct AnswerverifiedShow Answer

Which of the following is true regarding hydrogen bonds.

Correct AnswerverifiedD

Which of the following statements about hydrogen bonds is false?

Correct AnswerverifiedShow Answer

The ratio of a weak acid and its conjugate base at the point of maximum buffering capacity is

Correct AnswerverifiedShow Answer

Is water an acid or a base?

Correct AnswerverifiedShow Answer

Which of the following is not true?

Correct AnswerverifiedA

Which of the following molecules is amphipathic?

Correct AnswerverifiedShow Answer

Which of the following is true?

Correct AnswerverifiedShow Answer

A micelle is a structure which

Correct AnswerverifiedShow Answer

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C

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The dissociation constant for an acid with a pK_a value of 6.0 is

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For an acid that undergoes this reaction: HA ↔ H⁺ + A− K_a =

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D

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A

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