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Finals > Chemistry > Flashcards

Chemistry Flashcards

1
Q

What are acids?

A

Molecules/ions that give up protons in solution

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2
Q

What is the reaction for acids in solution?

A

HX –> H+ + X-

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3
Q

What is the ionisation reaction for water?

A

H2O <–> H+ + OH-

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4
Q

What is the ionisation reaction for acetic acid?

A

CH3COOH <–> H+ + CH3COO-

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5
Q

What are bases?

A

A molecule/ion that acquire protons in solution

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6
Q

What is the reaction for bases in solution?

A

X- + H+ –> HX

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7
Q

What is the ionisation reaction for the hydroxyl ion in bases?

A

OH- + H+ –> H2O

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8
Q

What is the ionisation reaction for the acetate ion in bases?

A

CH3COO- + H+ <–> CH3COOH

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9
Q

What is the ionisation reaction for ammonia in bases?

A

NH3+ + H+ <–> NH4+

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10
Q

What is the ionisation reaction for amines in bases?

A

R-NH2 + H2 <–> R-NH3+

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11
Q

What is the conjugate acid and base in:m
HX <—> H+ + X-

A

Conjugate acid= HX
Conjugate base= X-

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12
Q

What is the equation for Ka?

A

([H+][X-])/[HX]

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13
Q

What is the effect of a larger pKa?

A

The larger the pKa, the smaller the extent of dissociation

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14
Q

What is the dissociation constant?

A

A quantitive measure of the strength of acid in solution

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15
Q

What is Ka?

A

The acid dissociation constant

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16
Q

What is the Ka of water?

A

Ka= 1.8 x 10 ^-16

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17
Q

What is the equation for pH?

A

pH= log10[H+]

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18
Q

What is the dissociation reaction for carbonic acid?

A

H2CO3 <—> H+ + HCO-

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19
Q

What is the pKa of carbonic acid?

A

6.37

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20
Q

When is carbonic acid formed in humans?

A

When CO2 dissolves in blood tissue fluids

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21
Q

What is the function of carbonic acid in blood at a physiological pH?

A

Buffer

22
Q

What is the dissociation reaction of lactic acid?

A

CH3CH(OH)COOH <—> H+ + CH3CH(OH)COO-

23
Q

When is lactic acid formed?

A

By human cells from glucose during anaerobic respiration, especially in muscles during rapid movement

24
Q

What is the pKa of lactic acid?

A

3.86

25
Q

What does lactic acid cause?

A

Cramp

26
Q

How is lactic acid converted into glucose?

A

Gluconeogenesis in the liver (Cori cycle)

27
Q

What is the dissociation reaction for hydrochloric acid?

A

HCl <—> H+ + Cl-

28
Q

What is the function of hydrochloric acid in the body?

A

Secreted into the stomach for digestion

29
Q

What is the pKa of hydrochloric acid?

A

<1

30
Q

What are examples of acids produced by oral bacteria?

A

Lactic acid
Formic acid
Acetic acid
Propionic acid
Butyric acid

31
Q

What is the fomula and pKa of formic acid?

A

HCOOH
pKa= 3.75

32
Q

What is the fomula and pKa of acetic acid?

A

CH3COOH
pKa= 4.73

33
Q

What is the fomula and pKa of propionic acid?

A

CH3CH2COOH
pKa= 4.87

34
Q

What is the fomula and pKa of butyric acid?

A

CH3CH2CH2COOH
pKa= 4.82

35
Q

What is the equation for the dissociation of calcium phosphate (hydroxyapatite) by acids?

A

Ca10(PO4)6(OH)2 + 8H+ <—> 10Ca2+ + 6HPO4 2- +2H2O

Ca10(PO4)6(OH)2 + 14H+ <—> 10Ca2+ + 6H2PO4- + 2H2O

36
Q

Discuss the effect of shifts to left/right in the dissociation of calcium phosphate?

A

An increase in [H+] causes there equilibrium to shift to the right, increasing the solubilisation of calcium phosphate

An increase in calcium or phosphate concentration causes the equilibrium to shift to the left inhibiting solubilisation and promoting remineralisation

37
Q

What is the role of saliva in regard to calcium phosphate dissocation?

A

Saliva contains calcium and phosphate to aid remineralisation

38
Q

What is the pH of acidic drinks?

A

2-4

39
Q

What do organic acids act as?

A

Chelating agents: bind strongly to divalent and trivalent cations
Bind calcium ions which are then no longer available to counteract calcium solubilisation and contributes to tooth erosion

40
Q

What is a buffer?

A

Consist of similar concentration of the conjugate acid or conjugate base
Made by neutralising the an acid with OH- or mixing together a solution of acid and one of its salt at an appropriate Ka

41
Q

What is the % dissociation at maximum buffering capacity?

A

50%

42
Q

What is the Henderson-Hasselbalch equation?

A

pH= pKa + log10 (salt/acid)

43
Q

Where does a buffer have effective buffering capacity?

A

Within +/- pH unit of its pKa

44
Q

What is the main buffer in saliva?

A

HCO3- (bicarbonate)

45
Q

What other factors contribute to the buffering capacity of saliva?

A

Phosphate
Protein

46
Q

Where does the bicarbonate in saliva come from?

A

Blood
Action of carbonic anhydrous (enzyme that forms carbonic acid)- carbonic acid dissociates into hydrogen and bicarbonate

47
Q

What pH is the major buffering capacity of saliva?

A

6.7

48
Q

What are the three equilibria and their pKa for phosphate as a buffer?

A

H3PO4 <—> H+ + H2PO4 (pKa=2.16)
H2PO4- <—> H+ +HPO4 2- (pKa=7.21)
HPO4 2- <—> H+ +PO4 3- (pKA=12.32)

49
Q

What are examples of salivary proteins that have carboxylic acids in their side chain?

A

Aspartic acid
Glutamic acids

50
Q

What is an example of a salivary protein that has an imidazole side chain?

A

Histidine

51
Q

What is the pH of blood?

A

7.4

52
Q

What are the buffers in blood?

A

Bicarbonate and protein buffers

Finals (20 decks)

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