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Chemistry 101 COPY > Buffers > Flashcards

Buffers Flashcards

1
Q

What is the pH of blood maintained by?

A

Carbonic acid and its conjugate base (bicarbonate)

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2
Q

Is carbonic acid a strong acid or a weak acid?

A

A weak acid

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3
Q

What occurs to blood pH during severe anxiety attacks?

A

It increases

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4
Q

What occurs to blood pH during exercise?

A

It increases

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5
Q

What does it mean that blood is buffered?

A

The pH is regulated

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6
Q

What does it mean in a practical sense if something is buffered?

A

The concentration of hydronium ions is controlled

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7
Q

What does the loss of hydronium ions result in, in terms of pH?

A

A lower pH

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8
Q

What do most chemical reactions in the body involve?

A

pH-dependent proteins

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9
Q

What is the pH of blood?

A

7.4

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10
Q

What is the pH of blood maintained by?

A

Buffers dissolved in blood

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11
Q

Is there only one form of buffer in the blood, or a variety?

A

There are a variety

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12
Q

What does a buffer ensure when a solution has hydronium or hydroxide ions added or removed?

A

That the pH of the solution doesn’t change

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13
Q

What can H+ ions be considered?

A

Acid

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14
Q

What are buffers generally made up of?

A

A weak acid and its conjugate base (salt)

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15
Q

Can buffers be made up of a weak base and its conjugate acid?

A

Yes, but usually not

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16
Q

Why do buffers work?

A

As the concentration of the weak acid and its salt are large compared to the amount of protons or hydroxide ions added or removed.

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17
Q

What occurs to the buffer if protons are added to a solution?

A

The base component of the buffer is converted to the acid

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18
Q

What occurs to the buffer if hydroxide ions are added to a solution?

A

The acid component of the buffer is converted to the base

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19
Q

What is the mechanism of the reaction of buffers when protons are added to the solution?

A

H3O+ + A- -> H2O + HA

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20
Q

What is the mechanism of the reaction of buffers when hydroxide ions are added to the solution?

A

OH- + HA -> H2O + A-

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21
Q

How do you know which to use out of H+ and H3O+?

A

They are the same. You can use them interchangably

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22
Q

What is the pH of blood dependent on?

A

Only the ratio of CO2 to HCO3- present in the blood

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23
Q

When does optimal buffering occur?

A

When pH is within 1 pH unit of the pKa

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24
Q

What is the pKa of carbonic acid?

A

6.1

25
Q

What is the optimal buffer region of carbonic acid?

A

5.1-7.1

26
Q

How does carbonic acid work in blood (pH 7.4) if its optimal buffer region is 5.1-7.1?

A

As the full reaction is not completely an acid-base reaction, there is also a dissociation reaction.

27
Q

What is the acid/base equilibrium of the carbonic acid-bicarbonate buffer in blood?

A

H+(aq)+HCO3-(aq)<=>H2CO3(aq)+H2O(l)

28
Q

What does H+ act as in the carbonic acid-bicarbonate buffer in blood?

A

The conjugate acid

29
Q

What does HCO3- act as in the carbonic acid-bicarbonate buffer in blood?

A

The conjugate base

30
Q

What does H2CO act as in the carbonic acid-bicarbonate buffer in blood?

A

The acid (Carbonic Acid)

31
Q

What does H2O act as in the carbonic acid-bicarbonate buffer in blood?

A

The base

32
Q

What is the dissociation reaction of the carbonic acid-bicarbonate buffer in blood?

A

H2CO3(aq)+H2O(l)<=>2H2O(l)+CO2(g)

33
Q

How do the kidneys help to control the pH of the blood?

A

Kidneys remove H+ (lowers pH) and excess HCO3- ions from blood

34
Q

Do the kidneys change the pH of blood quickly or slowly?

A

Slowly

35
Q

How do the lungs help to control the pH of the blood?

A

By removing excess CO2 (increasing pH)

36
Q

Do the lungs change the pH of blood quickly or slowly?

A

Quickly

37
Q

What is the overall reaction for the carbonic acid-bicarbonate buffer in blood?

A

H+(aq)+HCO3-(aq)<=>H2CO3(aq)+H2O(l)<=>2H2O(l)+CO2(g)

38
Q

What side of the carbonic acid-bicarbonate buffer in blood is controlled by the kidneys (through secretion in the urine)?

A

H+(aq)+HCO3-(aq)<=>H2CO3(aq)+H2O(l)

39
Q

What side of the carbonic acid-bicarbonate buffer in blood is controlled by the lungs (through expulsion in air)?

A

H2CO3(aq)+H2O(l)<=>2H2O(l)+CO2(g)

40
Q

Why is buffering capacity greatest when the pH is near the pKa?

A

Because, in this region, a shift in the relative concentrations of bicarbonate and carbon dioxide produces only a small change in the pH of the solution

41
Q

What formula can be used to calculate the pH of a buffer solution?

A

The Henderson-Hasselbalch equation

42
Q

What is the formula for the Henderson-Hasselbalch equation?

A

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

43
Q

What two things is the Henderson-Hasselbalch equation used to do?

A

Calculate the pH of a solution created from known amounts of acid and its conjugate base Relate pH with pKa

44
Q

How do you determine which substance is HA and which is A-?

A

The acid is HA

45
Q

If the concentration of HA is greater than the concentration of A-. should the pH be higher or lower than the pKa?

A

It should be lower than the pKa

46
Q

If the concentration of HA is greater than the concentration of A-. should the pH be higher or lower than when the solution is at equilibrium?

A

It should be lower than when the solution is at equilbrium

47
Q

How does pKa relate to pH?

A

The pKa is the pH of a solution when it is at equilibrium

48
Q

What does p mean?

A

The negative log of something

49
Q

If the concentration of A- is greater than the concentration of HA, should the pH be higher or lower than the pKa?

A

It should be higher than the pKa

50
Q

If the concentration of A- is greater than the concentration of HA, should the pH be higher or lower than when the solution is at equilibrium?

A

It should be higher than when the solution is at equilbrium

51
Q

What are the 5 steps for the preparation of buffers?

A

Know the pH you want.

The pKa of the buffer must not differ more than one unit from this value.

Choose the buffer to suit

Use the Henderson-Hasselbalch equation to work out the ratio of acid and conjugate base you need.

Use the molecular weight to work out the mass of each part you need

52
Q

What is the pKa of acetic acid?

A

4.76

53
Q

What does the colour change of an acid base indicator depend on?

A

The the pKa

54
Q

Draw the structure of Acetic Acid

A
55
Q

Draw the structure of pyridine

A
56
Q

Draw the structure of HEPES

A
57
Q

What is the molecular formula of Dihydrogen phosphate?

A

H2PO4-

58
Q

Draw the structure of phenol

A
59
Q

Draw the structure of Lactic Acid

A

Chemistry 101 COPY (32 decks)

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