Acids, Bases, pHs, and Buffers

Question 1

Under what conditions is a buffer most effective?

Answer 1

when the concentration of a weak acid and its conjugate base are equal

Question 2

A solution that resists changes in pH when perturbed by the addition of an acid or base

Answer 2

buffer

Question 3

How can the bicarbonate system be simplified?

Answer 3

CO2 H+ + HCO3-

Question 4

What is K/K(eq)?

Answer 4

[products]
________
[reactants]

forward and reverse rates are equal

Question 5

Using magnitudes of K, what are the predicted concentrations of products and reactants?

Answer 5

Small K (<10^-3) = more reactants than products
Intermediate K (10^-3 - 10^3) = equal amount of reactants and products
Large K (>10^3) = more products than reactants

Question 6

______ acids have large values for K

Answer 6

strong

Question 7

pKa

Answer 7

-logKa

pH at which the weak acid/base is 50% ionized/50% unionized

Question 8

pH is a measure of …

Answer 8

H+

Question 9

pKa is a measure of…

Answer 9

dissociation

Question 10

a stronger acid acid has a _____ pH and a _____ pKa

Answer 10

lower; lower

Question 11

As the [H+] increases, pH ______

Answer 11

decreases

Question 12

As the dissociation increases, pKa _____

Answer 12

decreases

Question 13

If a molecule has a negative pKa, it has a ______ Ka

Answer 13

large

Question 14

If a molecule has a small Ka, what do we know about the concentrations of the products and reactants?

Answer 14

more reactants than products

Question 15

If a molecule has a small Ka, it has a _____ pKa

Answer 15

large

Question 16

Henderson-Hasselbalch (Definition)

Answer 16

relates the pH of a solution of a weak acid to the pKaand extent of ionization of that acid

Question 17

Henderson-Hasselbach (Equation)

Answer 17

pH = pKa + log([A]/[HA])
OR
pH = pKa + log([unprotonated]/[protonated])
OR
pH = pKa + log ([conjugate base]/[acid])

Question 18

______ can be referred to as unprotonated, charged, or ionized form

Answer 18

conjugate base

Question 19

______ can be referred to as protonated, uncharged, or unionized form

Answer 19

weak acid

Question 20

What does Ka reflect?

Answer 20

The ionization of the acid

Question 21

How is pKa related to buffering capacity?

Answer 21

indicates the pH where the substance will be most effective as a buffer – based on the side chain

Question 22

Can charged or uncharged pass through the membrane more easily?

Answer 22

small uncharged molecules