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Chemistry > 12.1 > Flashcards

12.1 Flashcards

1
Q

an acid is a proton…

A

donor

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2
Q

a base is a proton…

A

acceptor

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3
Q

when does a molecule which contains hydrogen act as an acid

A

if the hydrogen carries a slightly positive charge

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4
Q

what makes a molecule a base

A

it must contain a lone pair in order to form a dative covalent bond

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5
Q

what is a conjugated acid-base pair

A

consists of either a base and its conjugate acid or an acid and its conjugated base

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6
Q

state the conjugated pairs for this reaction
HCl + H2O <=> H3O+ + Cl-

A

Cl- & HCl
H2O & H3O+

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7
Q

what is meant by monoprotic

A

a species that can donate 1 proton

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8
Q

what is meant by diprotic

A

a species that can donate 2 protons

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9
Q

what is an amphoteric substance

A

one that can act both as an acid and as a base

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10
Q

how do you define a strong acid

A

one that almost completely dissociates in aqueous solutions

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11
Q

how do you define a weak acid

A

one that only partially dissociates in aqueous solutions

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12
Q

what is the equation for pH

A

pH = -log[H+]

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13
Q

what does Ka stand for

A

acid dissociation constant

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14
Q

what is the general equation for Ka

A

Ka = [H+(aq)] [A-(aq)] / [HA(aq)]

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15
Q

what is the equation for Ka in strong acids

A

Ka = [H+(aq)] / [HA(aq)]

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16
Q

what is the equation for pKa

A

pKa = -logKa

17
Q

How does pKa and Ka effect the pH of an acid

A

as Ka increases pH decreases
as pKa decreases pH decreases

18
Q

what is the equation for self-ionization of water

A

Kw = [H+(aq)] [OH-(aq) / [H2O(l)]

19
Q

How is the equation for ionisation of water simplified at a stated temperature

A

Kw = [H+(aq)] [OH-(aq)]

20
Q

what does Kw stand for

A

the ionic product of water

21
Q

how do you define a neutral solution

A

one in which the hydrogen ion concentration is equal to the hydroxide ion concentration

22
Q

what is the equation for pKw

A

pKw = -log Kw

23
Q

why do even the most alkaline solutions still contain some hydrogen ions

A

because of the fact that water self-ionises

24
Q

how can the relative strengths of different acids or bases be determined

A

by measuring the pH of equimolar aqueous solutions of the acids/bases, at the same temperature

25
Q

what is the pH of a salt formed from a strong acid and a strong base

A

7

26
Q

what is the pH of a salt formed from a weak acid and a strong base

A

> 7

27
Q

what is the pH of a salt formed from a strong acid and a weak base

A

<7

28
Q

what is the pH of a salt formed from a weak acid and a weak base

A

dependent on the relative strengths of the acid and base

29
Q

how is pH effected when a strong acid is diluted by a factor of 10

A

pH increases by a factor of 1 for each 10-fold decrease in concentration

30
Q

how is pH effected when a weak acid is diluted by a factor of 10

A

pH value increases by a factor of about 0.5 for each 10-fold decrease in concentration

31
Q

how can Ka of a weak monobasic acid such as benzoic acid by determined experimentally

A

accurately weigh between 0.4-0.5g of the acid
dissolve it in roughly 50cm^3 of deionised water
transfer solution to a 250cm^3 volumetric flask and add washings from the beaker using deionised water to make the solution up to the mark
mix by inverting the flask then withdraw a sample and use a calibrated pH meter to measure the pH of the solution
then caluclate the Ka value

32
Q

what are the issues with calculating Ka experimentally

A

you must assume that the concentration of the acid at equilibrium is identical to the original concentration of the acid however it is not as it may have dissociated slightly
the accuracy of the measurement of pH as this largely effects the Ka calculated due to small amounts being used

Chemistry (46 decks)

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