Acids, bases and buffers Flashcards

1
Q

what are Bronstead Lowry acids

A

proton donors

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2
Q

what do H+ ions form in water

A

hydroxonium ions

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3
Q

what are Bronsted Lowry bases

A

proton donors

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4
Q

what is called when an acid can donate more than one proton and give examples

A

polyprotic
nitric acid
sulphuric acid
phosphoric acid

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5
Q

acids react with bases to form _______ which are pH _____

A

salts pH

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6
Q

what is a conjugate pair linked by

A

transfer of a proton

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7
Q

any species that has gained a proton is a conjugate _____ and any species which has lost a proton is a conjugate ______

A

acid, base

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8
Q

when a strong acid or base is present the forward or backward reaction is favoured? and more ions are produced

A

forward

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9
Q

what is the equation for Kw

A

Kw= (H+)(OH-)

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10
Q

how do you calculate pH

A

pH= -log10 (H+)

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11
Q

how do you calculate conc. of H+ ions

A

= 10^-ph

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12
Q

monoprotic acids dissociate to produce one H+ ion for every acid molecule, this means that

A

conc of the acid= conc of H+ ions

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13
Q

diuretic acids dissociate to produce two H+ ions for every acid molecule this means that

A

conc of acid= 2 x conc of H+ ions

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14
Q

weak acids only dissociate slightly in aqueous solutions so what constant is used to work out their pH

A

Ka

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15
Q

what are the two assumptions made when calculating Ka of a weak acid

A

only a small amount of weak acid dissociates
(conc of weak acid at equilibrium)= (conc of weak cid at start)
the dissociation of acid is greater than the dissociation of water so all H+ ions come from acid
H+ conc= A-

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16
Q

what is the calculation for pKa

A

pKa= -log10Ka

17
Q

what is the calculation for Ka using pKa

18
Q

when using a ph probe what must you do first

A

place in distilled water

19
Q

draw titration curve for a strong acid and strong base

20
Q

draw titration curve for strong acid weak base

21
Q

draw titration curve for weak acid strong base

22
Q

draw titration curve for weak acid weak base

23
Q

what is the equivalence point on a titration curve

A

when the acid has been fully neutralised by the base
H+ conc= OH- conc

24
Q

what must you look at on a titration curve when choosing a suitable indicator

A

the vertical part

25
when can methyl orange be used as indicator and what is its colour change
red at low pH, yellow at high strong acid, weak base strong acid, strong base
26
when can phenolphthalein be used as an indicator and what is its colour change
colourless at low ph, pink at high ph weak acid, strong base
27
what is a buffer solution
system that minimises pH changes on addition of small amounts of an acid or a base
28
how do you calculate the pH of a buffer
1. write equation and Ka expression 2. rearrange question to get H+ conc 3. calculate H+ 4. calculate ph using -log (H+)
29
how are buffers used in the blood
blood pH should be maintained at 7.4 H2CO3------H+ + HCO3- H2CO3-------- H2O+ CO2 when we breathe out CO2 the level of carbonic acid reduces as equilibrium shifts to the right to attempt to replace them
30