Deck 6: Acids and Bases

Question 1

What hybridization best stabilizes the negative charge of conjugate bases?

A)p
B)sp
C)sp²
D)sp³

Answer 1

sp

Question 2

Figure 1
Figure 1 is a list of pK_a values for various organic functional groups.
Referring to Figure 1,what is the most acidic proton in the following molecule?

A)Choice a
B)Choice b
C)Choice c
D)Choice d

Answer 2

Choice a

Question 3

Given the structure and pK_a of analine (shown below),what can be said about its protonation state at pH 4.9?

A)˜100%
B)˜100%
C)˜50% ,˜50%

D)There is not enough data to evaluate.

Answer 3

˜50% ,˜50%

Question 4

What is the definition of a Lewis base?

A)a proton donor
B)a proton acceptor
C)an electron donor
D)an electron acceptor

Question 5

What is the definition of a Brønsted acid?

A)proton donor
B)proton acceptor
C)electron donor
D)electron acceptor

Question 6

Given the structure and pK_a of 2,2,2 trifluoroethanol (shown below),what can be said about its protonation state at pH 10?

A)It will exist mostly in the protonated form.
B)It will exist mostly in the deprotonated form.
C)It will be 50% protonated and 50% deprotonated.
D)There is not enough data to evaluate.

Question 7

Which acid shown below is stronger and why?

A)A due to charge delocalization
B)B due to charge delocalization
C)A due to induction
D)B due to induction

Question 8

Which acid shown below is stronger and why?

A)A due to atomic size
B)B due to atomic size
C)A due to electronegativity
D)B due to electronegativity

Question 9

Which acid shown below is stronger and why?

A)A due to charge delocalization
B)B due to charge delocalization
C)A due to hybridization
D)B due to hybridization

Question 10

What is the role of induction in conjugate base stability?

A)Larger atoms are better capable of dispersing the negative charge of the conjugate base.
B)Electronegative atoms are better able to carry negative charge.
C)Neighbouring electronegative groups can help distribute charge over a wider area.
D)Higher s character helps stabilize negative charge.

Question 11

Given the structure and pK_a of pyridine (shown below),what can be said about its protonation state at pH 7?

A)It will exist mostly in the protonated form.
B)It will exist mostly in the deprotonated form.
C)It will be 50% protonated and 50% deprotonated.
D)There is not enough data to evaluate.

Question 12

Which side will the equilibrium of the following acid/base reaction lie and why?

A)to the left because ethoxide is a stronger base than acetate
B)to the left because acetate is a stronger base than ethoxide
C)to the right because ethoxide is a stronger base than acetate
D)to the right because acetate is a stronger base than ethoxide

Question 13

What is the role of atomic size in conjugate base stability?

A)Larger atoms can disperse developed charge better than smaller atoms,making them better acids.
B)Smaller atoms can disperse developed charge better than larger atoms,making them better acids.
C)Larger atoms can disperse developed charge better than smaller atoms,making them worse acids.
D)Smaller atoms can disperse developed charge better than larger atoms,making them worse acids.

Question 14

Which of the following best describes BF₃?

A)Brønsted acid
B)Brønsted base
C)Lewis acid
D)Lewis base

Question 15

What characterizes weak acids in comparison to strong acids?

A)a larger K_a and a larger pK_a
B)a larger K_a and a smaller pK_a
C)a smaller K_a and a larger pK_a
D)a smaller K_a and a smaller pK_a

Question 16

Which acid shown below is stronger and why?

A)A because nitrogen is more electronegative
B)A because oxygen is more electronegative
C)B because nitrogen is more electronegative
D)B because oxygen is more electronegative

Question 17

Which is the most acidic proton in the molecule shown below?

A)The methyl proton is the most acidic.
B)The amino proton is the most acidic.
C)The hydroxyl proton is the most acidic.
D)All groups are equally acidic is the most acidic.

Question 18

Which of the phenols shown below is the stronger acid,and why?

A)A,because the chloride groups are inductively electron donating
B)A,because the chloride groups are inductively electron withdrawing
C)B,because the methyl groups are inductively electron donating
D)B,because the methyl groups are inductively electron withdrawing

Question 19

Rank these compounds in order of increasing basicity.(Least basic to most basic)

A)C,B,A
B)B,A,C
C)C,A,B
D)A,B,C

Question 20

Figure 1
Figure 1 is a list of pK_a values for various organic functional groups.
Referring to Figure 1,on what side of the equilibrium will the following reaction lie?

A)the left,because water has a higher pK_a than thioethane
B)the right,because water has a higher pK_a than thioethane
C)the left,because hydronium has a lower pK_a than thioethane
D)the right,because hydronium has a lower pK_a than thioethane

Question 21

Which molecule shown below would you expect to be most acidic and why?

A)A,due to charge delocalization
B)B,due to charge delocalization
C)A,due to hybridization
D)B,due to hybridization

Question 22

Given the following reaction scheme,what best describes ethanethiolate?

A)It is an acid.
B)It is a base.
C)It is a conjugate acid.
D)It is a conjugate base.

Question 23

Electron withdrawing groups stabilize conjugate bases.

Question 24

Which of the following best describes the molecules shown below?

A)A is the stronger base;B is the stronger acid.
B)A is the stronger acid;B is the stronger base.
C)A is the stronger base and the stronger acid.
D)B is the stronger base and the stronger acid.

Question 25

Rank the following molecules in terms of increasing acidity (from least to most).

A)A,B,C
B)C,B,A
C)B,C,A
D)A,C,B

Question 26

Given the following reaction scheme,what best describes water?

A)It is an acid.
B)It is a base.
C)It is a conjugate acid.
D)It is a conjugate base.

Question 27

Which of the following molecules is the stronger acid and why?

A)A,due to charge delocalization
B)B,due to charge delocalization
C)A,due to hybridization
D)B,due to hybridization

Question 28

A Lewis acid is an electron acceptor.

Question 29

Acidity increases going down the periodic table.

Question 30

Compound A has a pK_a of 10 and compound B has a pK_a of 5.How many times more acidic is compound B compared to A?

A)2 times more acidic
B)5 times more acidic
C)10 000 times more acidic
D)50 000 times more acidic

Question 31

Rank the labelled protons in the following molecule in order of increasing acidity (from least acidic to most acidic).

A)A,B,C
B)C,B,A
C)C,A,B
D)B,A,C

Question 32

Which proton is expected to be the most acidic in the molecule shown below?

A)a!
B)b!
C)c!
D)d!

Question 33

Which proton in the following molecule is more acidic and why?

A)A,because of charge distribution
B)A,because of hybridization
C)B,because of charge distribution
D)B,because of hybridization

Question 34

Which of the indicated protons in the following molecule is more acidic and why?

A)A,because of greater charge distribution
B)A,because of greater induction
C)B,because of greater charge distribution
D)B,because of greater induction

Question 35

Which of the following best describes the molecules shown below?

A)A is the stronger base;B is the stronger acid.
B)A is the stronger acid;B is the stronger base.
C)A is the stronger base and the stronger acid.
D)B is the stronger base and the stronger acid.

Question 36

A Brønsted base is a molecule that contains hydroxide.

Question 37

Rank the labelled amines in the following molecule in order of increasing basicity (from least basic to most basic).

A)A,C,B
B)C,B,A
C)C,A,B
D)B,A,C

Question 38

Given the following reaction scheme,which molecule is the base?

A)
B)
C)
D)

Question 39

Given the following reaction scheme,which molecule is the conjugate acid?

A)
B)
C)
D)

Question 40

Atoms with greater s character are better able to stabilize negative charge.

Question 41

Electronegativity is used to compare the acidity of atoms in the same row on the periodic table.

Question 42

Atomic size is used to compare the acidity of atoms in the same row on the periodic table.

Question 43

Atoms with greater electronegativity are better electron withdrawers through induction.

Question 44

The strength of a neutral acid is dependent on how well the charge is stabilized in the conjugate base.

Question 45

Neighbouring electron withdrawing groups will destabilize a positively charged atom.

Question 46

Reactions proceed in the direction of weak acid to strong conjugate acid.

Question 47

HClO₂ is a stronger acid then HClO₃.

Question 48

Strong acids tend to have negative ÄG values,whereas weak acids tend to have positive ÄG values.

Question 49

Alcohols are stronger bases than amines.

Question 50

Most organic acids are considered strong acids.

Question 51

The equilibrium of an acid/base reaction will favour the side with the higher acid pK_a.

Question 52

Carboxylic acids are more acidic than alcohols due to their enhanced ability to delocalize positive charge.

Question 53

Brønsted bases are not considered Lewis bases.

Question 54

Thiols are stronger acids than alcohols.

Question 55

Higher pK_a values lead to stronger acids.

Question 56

Alcohols are stronger acids than amines.

Question 57

The protonated state of a molecule dominates if the pH is less than the pK_a of a molecule.

Question 58

The strength of a base is independent of its conjugate acid's pK_a.

Question 59

Neighbouring alkyl groups will destabilize a positively charged atom.

Question 60

A carbocation is an example of a Lewis acid.

Question 61

A carbanion is an example of a Lewis _______________.

Question 62

Neighbouring _______________ groups stabilize a conjugate base through induction.

Question 63

Electronegative atoms are _______________ capable of carrying positive charge.

Question 64

Given the following reaction equilibrium and pK_a values,determine which direction is favoured.Identify each molecule as acid,base,conjugate acid,or conjugate base.

Question 65

Substituents on phenol can modulate its pK_a values.Explain the differences in pK_a seen in the three different phenol molecules shown below.Draw resonance structures to justify your answers.

Question 66

Sulfur is better at stabilizing negative charge compared to oxygen due to its _______________ .

Question 67

A molecule with an empty p orbital is an example of a(n)_______________ .

Question 68

Determine which side of the equilibrium is favoured in the following acid/base reaction shown below.Justify your answer.Indicate which is the acid,base,conjugate acid,and conjugate base.

Question 69

A molecule will be deprotonated If the pH is _______________ the pK_a of an acid.

Question 70

Tert-butanol is 100 times less acidic then ethanol (shown below).Explain why this is the case.

Question 71

A chemist mixes propanoic acid with one equivalent of a strong base,hoping to produce the following anion.Explain the error in the chemist's logic and show what product will actually be produced.

Question 72

Predict the products of the following acid/base reaction shown below.

Question 73

When considering atomic size,_______________ atoms are better able to handle positive charge.

Question 74

Would water be a suitable solvent for the following reaction? Why or why not.Water has a pK₃₅ of 14.

Question 75

Alkyl groups are considered inductively electron _______________ .

Question 76

Although similar constitutional isomers,salicylic acid is 50 times more acidic than p-hydroxybenzoic acid (shown below).Come up with a reason why this is the case,and draw a structure that verifies your hypothesis.

Question 77

Use resonance structures to explain the differences in pK_a of the two structures shown below.

Question 78

Oxygen is better able to stabilize negative charge compared to nitrogen due to its _______________ .

Question 79

The hydrogen atoms on the sp³-hybridized carbon are much more acidic then their sp²-hybridized counterparts in 1,3-cyclopentandiene,seemingly violating the rule that atoms with more s character are more acidic.Explain why this is the case.Draw a picture of the molecule to justify your answer.

Question 80

The stronger the acid,the _______________ the conjugate base.