Chapter 16 (sections 1-3)

Question 1

Define buffer

Answer 1

A solution containing significant amounts of both a weak acid and its conjugate base (or a weak base and its conjugate acid) that resists pH change by neutralizing added acid or added base

Question 2

A buffer resists pH change by _____ added acid or base.

Answer 2

neutralizing

Question 3

A buffer contains significant amounts of …?

Answer 3

both a weak acid AND its conjugate base (or a weak base and its conjugate acid)

Question 4

Buffers ____ pH change.

Answer 4

resist

Question 5

A____ contains significant amounts of both a weak acid and its conjugate base

Answer 5

buffer

Question 6

In a buffer the weak acid ____ added base until the concentration of the base…?

Answer 6

neutralizes

exceeds the concentration of the weak acid

Question 7

In a buffer, the conjugate base ____ the added acid until the concentration of the acid …?

Answer 7

neutralizes

exceeds the concentration of the conjugate base

Question 8

Define common ion affect

Answer 8

The tendency for a common ion to decrease the solubility of an ionic compound or to decrease the ionization of a weak acid or weak base

Question 9

Using the approximation that x is small we can consider the equilibrium concentrationd of HA and A- to be essentially …?

Answer 9

identical to the initial concentrations of HA and A-

Question 10

To determine the concentration of [H₃0⁺] for any buffer solution, we…?

Answer 10

multiply Ka by the ratio of the concentrations of the acid and the conjugate base
[H₃0⁺] = Ka [HA]/[A⁻]

Question 11

In a buffer solution where the concentrations of the acid and conjugate base are equal what is [H₃0⁺] equal to?

Answer 11

Ka

Question 12

When calculating the pH of a buffer, adding a small amount of strong acid to a buffer converts the stoichiometric amount of the _____ to the _____ ____

Answer 12

base

conjugate acid

Question 13

When calculating the pH of a buffer, adding a small amount of strong base to a buffer converts the stoichiometric amount of the _____ to the _____ ____

Answer 13

acid

conjugate base

Question 14

Define buffering action

Answer 14

The way a buffer solution reacts with small amounts of acid or base to maintain a fairly constant pH

Question 15

pKa + pKb =..?

Answer 15

14

Question 16

When is a buffer most effective?

Answer 16

When the concentrations of the acid and conjugate base are equal

Question 17

A buffer becomes less effective as the difference in relative amounts of acid and conjugate base ______.

Answer 17

Increases

Question 18

In order for a buffer to be reasonably effective, the relative concentrations of acid and conjugate base should not differ by more than a factor of _____.

Answer 18

10

Question 19

A buffer is most effective (most resistant to pH changes) when the concentrations of acid and conjugate base are ____.

Answer 19

high

Question 20

Lowest pH for effective buffers occurs when the base is one-tenth as concentrated as the acid. What is this in equation format?

Answer 20

pH = pKa -1

Question 21

Highest pH for effective buffer occurs when the base is 10 times as concentrated as the acid. What is this in equation format?

Answer 21

pH = pKa + 1

Question 22

The effective range for a buffering system is…?

Answer 22

one pH unit on either side of the pKa

Question 23

Define buffer capacity

Answer 23

the amount of acid or base that can be added to a buffer without destroying its effectiveness

Question 24

The buffer capacity increases with ____ absolute concentrations of the buffer components

Answer 24

increasing

Question 25

Overall buffer capacity increases as the relative concentrations of the buffer components become…?

Answer 25

more similar to each other

Question 26

As the ratio of the buffer components gets closer to one, the overall capacity of the buffer becomes _____.

Answer 26

greater