Ch. 3-Ionization of Drugs

Question 0

What does the pH scale measure, and what numbers on the scale correspond?

Answer 0

it measures how acidic or basic a substance is
-scale from 0 to 14
7=neutral
0-6=acidic
8-14=basic

Question 1

What does pH stand for?

Answer 1

power of hydrogen

Question 2

How are the concentration of hydrogen ions and pH related?

Answer 2

• the higher the concentration of H ions, the lower the pH (acidic)
• the lower the concentration of H ions, the higher the pH (basic)

Question 3

If one solution has a pH of 6 and another solution has a pH of 5, which one has more H ions?

Answer 3

solution with pH of 5 has more H ions and is therefore more acidic

Question 4

1 degree difference in pH equals how much of a difference in H ion concentration?

Answer 4

10x difference

-ex) solutions with pH’s of 5 and 6 have 10x difference, with pH of 5 and 7 have 100x difference

Question 5

acid

Answer 5

“donor”

it donates H ions to a base

Question 6

base

Answer 6

“recipient”

it receives H ions from the acid

Question 7

What is the normal pH of human blood, and what happens if it were to change?

Answer 7

7.35-7.45 (slightly basic)

if the pH changes the drug would become ionized, and it is impossible for ionized drug to cross cell membrane

Question 8

buffers

Answer 8

“shock absorbers”
prevent pH changes in the body when H ions are added or removed
-extracellular buffers and intracellular buffers

Question 9

major and minor extracellular buffer

Answer 9

1. HCO3- (bicarbonate, major)

2. phosphate (urinary buffer, minor)

Question 10

major and minor intracellular buffers

Answer 10

1. hemoglobin (major)
2. organic phosphate
3. proteins

Question 11

How do buffers work?

Answer 11

acid lowers the pH, so it would react with the base bicarbonate (HCO3-) to turn the acid into a weak acid
-base reacts with carbonic acid (H2CO3) to turn the base into a weak base

Question 12

What two buffers are a pair and are always present in the system?

Answer 12

bicarbonate (HCO3-) and carbonic acid (H2CO3)

Question 13

bicarbonate

Answer 13

HCO3-

reacts with acids to make them weaker

Question 14

carbonic acid

Answer 14

H2CO3

reacts with bases to make it a weak base

Question 15

weak acid

Answer 15

partially dissociates in water
thiopental and barbiturates
-more nonionized when H increases (lower pH)
-more ionized when H decreases (higher pH)
——-charge goes up and down with pH level

Question 16

weak base

Answer 16

local anesthetics
partially dissociate in water
-more nonionized when H decreases (higher pH)
-more ionized when H increases (lower pH)
——charge goes up or down with H concentration

Question 17

titration curve

Answer 17

describes how pH changes when H is added or removed

• H added=HA form, lowers pH, more acidic
• H removed=A- form, raises pH, more basic

Question 18

pK of a solution

Answer 18

when both sides of reaction are in equilibrium-there are equal numbers of ionized and nonionized ions
-also located at center of titration curve

Question 19

strong acids

Answer 19

completely dissolve in water

common acids-H2SO4 (sulfuric acid), HCl (hydrochloric acid), and HNO3 (nitric acid)

Question 20

strong bases

Answer 20

completely dissociate in water

NaOH (sodium hydroxide), KOH (potassium hydroxide), and Ca(OH)2 (calcium hydroxide)

Question 21

law of mass action

Answer 21

characterizes chemical equilibrium