L3 Water Part 2 of 2

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Question #1

The equivalence point of a titration is also called the end point.

A FALSE

B TRUE

Question #2

The slope of a titration curve is shallow within one pH unit of the pKa value.

A FALSE

B TRUE

Question #3

When a weak acid is 50% dissociated, pH of the solution is equal to the pKa of the acid.

A FALSE

B TRUE

Question #4

The titration curve of acetic acid has two buffering regions.

A TRUE

B FALSE

Question #5

Acetic acid is mostly protonated a pH = 2

A FALSE

B TRUE

Question #6

Acetic acid is mostly protonated at pH = 7.

A TRUE

B FALSE

Question #7

Phosphoric acid has three pKas.

A TRUE

B FALSE

Question #8

The pKa of acetic acid is 4.76. That means that at pH = 4.76, acetic acid is half dissociated.

A TRUE

B FALSE

Question #9

The equivalence point allows us to determine the pKa of an unknown acid.

A FALSE

B TRUE

Question #10

A the equivalence point the molar concentration of the proton donor equals the molar concentration of the proton acceptor.

A TRUE

B FALSE

Question #11

At the equivalence point, 50% of a weak acid titrated with a strong base is neutralized and converted to its conjugate base.

A TRUE

B FALSE

Question #12

The value of the equivalence point of titration of a weak acid with a strong base varies depending on the pKa of the acid.

A FALSE

B TRUE

Question #13

The equivalent point of a titration of a strong base with a strong acid occurs at pH = 7

A FALSE

B TRUE

Question #14

An acid-base titration is a neutralization reaction.

A TRUE

B FALSE

Question #15

A titration is an acid-base reaction, in which the hydrogen ions (H+) from the acid react with hydroxide ions (OH-) from the base to form a salt.

A FALSE

B TRUE

Question #16

For any weak acid-strong base titration, the pH at the equivalence point will be lesser than 7.

A FALSE

B TRUE

Question #17

At the midpoint of the titration, one-half of the original acid has undergone dissociation, so that the concentration of the proton donor equals that of the proton acceptor.

A TRUE

B FALSE

Question #18

Weak acids act as back up source of protons.

A FALSE

B TRUE

Question #19

Equivalence point = [acid] and [conjugate base] are equal.

A TRUE

B FALSE

Question #20

The slope of a titration curve is steep within one pH unit of the pKa value.

A FALSE

B TRUE

Question #21

At the mid point of titration, volume of analyte volume of titrant are not necessarily equal.

A TRUE

B FALSE

Question #22

Identify all the correct statements about an acid–base buffer solution.
I. It can be prepared by combining a strong acid with a salt of its conjugate base.
II. It can be prepared by combining a weak acid with a salt of its conjugate base.
III. It can be prepared by combining a weak base with its conjugate acid.
IV. The pH of a buffer solution does not change when the solution is diluted.
V. A buffer solution resists changes in its pH when an acid or base is added to it.

A I, II, IV, and V

B II, III, and IV

C II, III, IV, and V

D II, III, and V

E I, II, and IV

Question #23

At values of pH above the pKa value, an acid is mostly deprotonated.

A TRUE

B FALSE

Question #24

When an acetic acid solution is titrated with sodium hydroxide, the slope of the titration curve (pH vs volume of NaOH added) increases when sodium hydroxide is first added. This change shows that __________.

A a more concentrated solution of NaOH needs to be present to initiate the reaction.

B the pH is not affected until all the acetic acid is consumed.

C nothing is happening during this part of the titration.

D acetic acid is being converted to sodium acetate.

Question #25

What is the pH of a buffer solution where [HA] = [A–]?

A pH = pOH

B pH = 7.0

C pH = pKa

D pH = 1

Question #26

The ratio of the concentration of a ________ over ________ describes the proportions of forms of a weak acid necessary to satisfy the Henderson-Hasselbalch equation.

A conjugate acid; conjugate base and proton donor; proton acceptor

B conjugate base; conjugate acid and proton acceptor; proton donor

C conjugate base; conjugate acid and proton donor; proton acceptor

D conjugate acid; conjugate base and proton acceptor; proton donor

Question #27

Two weak acids, A and B, have pKa values of 4 and 6, respectively. Which statements true?

A For solutions of equal concentration, acid B will have a lower pH

B The equivalence point of acid A is higher than that of acid B

C Acid A dissociates to a greater extent in water than acid B

D B is the conjugate base of A

E Acid A is more likely to be a polyprotic acid than acid B

Question #28

In a titration of monoprotic acids and bases, there is a large change in pH __________

A at the point where pH = pKb of the base

B at the point where pH = pKa of the acid

C when the number of moles of acid is exactly equal to the number of moles of base

D when the volume of acid is exactly equal to the volume of base

Question #29

Water can act as an acid or a base.

A TRUE

B FALSE

Question #30

An initial pH of 9.5 and an equivalence point at pH 4.5 correspond to a titration curve for a

A strong base to which strong acid is added

B strong acid to which strong base is added

C weak base to which strong acid is added

D weak acid to which strong base is added

Question #31

Which of the following statements about buffers is true?

A At pH values lower than the pKa, the salt (conjugate base) concentration is higher than that of the acid.

B The pH of a buffered solution remains constant no matter how much acid or base is added to the solution.

C When pH = pKa, the weak acid and conjugate base concentrations are equal.

D The strongest buffers are those composed of strong acids and strong bases.

Question #32

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 H2PO4–

B H3PO4

C PO43–

D HPO42–

E none of the above

Question #33

The effectiveness or capacity of a buffer solution can be affected by

A molar concentration of the buffer components and concentration of the conjugate base to the weak acid

B temperature of buffer components and concentration of the conjugate base to the weak acid

C temperature of buffer components and molar concentration of the buffer components

Question #34

Polyprotic acids such as H3PO4, can act as acid-base buffers

A if their concentration is kept low

B only in combination with polyprotic bases

C at pH values around neutrality

D at pH values around any of their pKa’s

Question #35

What is the concentration, in moles/liter, of the hydrogen ion, if pH of a solution is 7?

A 1 x 10^-7

B 5 x 10^-7

C 7 x 10^-7

D 7

Question #36

What is the ratio of [A-]:[HA] in a solution at pH 5 that contains a weak acid with pKa = 5?

A 2;1

B 10:1

C 1:10

D 1:1

E 1:2

Question #37

A Bronsted acid becomes __________ upon losing a proton.

A its conjugate acid

B highly reactive

C its conjugate base

D a hydronium ion

Question #38

Buffer solutions

A tend to maintain a relatively constant pH.

B cause a decrease in pH when acids are added to them.

C are rarely found in living systems

D will always have a pH of 7

Question #39

At the mid point of titration, the ratio of the concentration of the weak acid with its conjugate base

A equals 1

B is 50:50

C is 1:1

D all of these

Question #40

A buffered solution

A Has a pH close to 7

B Has a zero average charge

C Resists changes in pH

D Has a pKa close to 7

Question #41

Acetate is a relative strong base.

A FALSE

B TRUE

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L3 Water Part 2 of 2

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