Acids and bases

Question 1

Define acidosis

Answer 1

A process causing increased acidity in the blood and other body tissues. If not further qualified, it usually refers to acidity of the blood plasma.

Question 2

What is the blood pH below when acidosis occurs?

Answer 2

7.35

Question 3

Define alkalosis

Answer 3

The result of a process reducing hydrogen ion concentration of arterial blood plasma

Question 4

What is the blood pH above when alkalosis occurs?

Answer 4

7.45

Question 5

What is the range of normal physiological pH?

Answer 5

7-7.5

Question 6

Where is it likely that the pH is outside the normal range?

Answer 6

Stomach- due to the stomach acids

Pancreas- due to pancreatic juice

Question 7

Write the equation for the dissociation of water.

Answer 7

H2O ⇌ H+ + OH-

Question 8

What’s the concentration of hydrogen ions in pure water at 25°C?

Answer 8

10^(-7) M

Question 9

How is pH calculated?

Answer 9

-log10([H+])

Question 10

Write the equation for Kw.

Answer 10

Kw=[H+][OH-]

Question 11

Give the value of Kw

Answer 11

10^-14 M^2

This is because [H+] and [OH-] in pure water are both 10^-7

Question 12

Define the term ‘acid’

Answer 12

A proton donor.

Question 13

Define the term ‘base’

Answer 13

A proton acceptor

Question 14

Define the term ‘conjugate base’

Answer 14

The chemical formed when an acid ionises

Question 15

Define the term ‘conjugate acid’

Answer 15

The acid formed when a base binds to a proton

Question 16

Write the ionisation equilibrium for a weak acid

Answer 16

HA ⇌ H+ + A-

Question 17

What is the formula for the equilibrium constant, Ka?

Answer 17

Ka= [H+][A-]/[HA]

Question 18

What does the size of Ka indicate about the strength of an acid?

Answer 18

The larger the Ka value, the stronger the acid

Question 19

How is pKa worked out?

Answer 19

pKa= -log10(Ka)

Question 20

What is the Henderson-Hasselbalch equation?

Answer 20

pH= pKa + log([A-]/[HA])

Question 21

When does pH=pKa?

Answer 21

When [HA]=[A-] because it means that the log([A-]/[HA]) =0

Question 22

When is pH smaller than pKa?

Answer 22

When there is more HA in solution

Question 23

When is pH larger than pKa?

Answer 23

When there is more A- in solution

Question 24

Define the term ‘buffer’

Answer 24

A substance that resists a change in pH when a small amount of acid or base is added

Question 25

When do acids and bases act as buffers?

Answer 25

When the pH is close to its pKa (+/- 1 pH unit)

Question 26

How do buffers work?

Answer 26

If the pH decreases, the base can accept H+, shifting the equilibrium to the left. If the pH increases, the acid can release H+, shifting the equilibrium to right

Question 27

Name the acid buffer that keeps the blood pH at 7.4

Answer 27

Carbonic acid

Question 28

Give the equation for carbonic acid acting as a buffer

Answer 28

CO2 + H2O ⇌ H2CO3 ⇌ H+ + [HCO3]-

Question 29

How can the body get rid of excess carbon dioxide?

Answer 29

Compensatory respiratory alkalosis (exhalation)