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EDEXCEL Chemistry a level > T12 Acid-base equilibria > Flashcards

T12 Acid-base equilibria Flashcards

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1
Q

acids

A

proton donors, releasing H + ions in water to form hydroxonium ions (H3O+)

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2
Q

bases

A

proton acceptors

take H+ ions from water molecules in solution to form OH- ions

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3
Q

strong acids /bases

A

dissociate completely in water

e.g HCl/ NaOH

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4
Q

weak acids/bases

A

dissociate partially in water

forms an equilibrium lying to the left

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5
Q

conjugate pairs

A

species linked by the transfer of a proton

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6
Q

conjugate base

A

species that has lost a proton

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7
Q

conjugate acid

A

species that has gained a proton

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8
Q

neutralisation reactions

A

when acids and base react together to form water and a salt.

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9
Q

neutral solution

A

equal conc of H+ and OH- ions

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10
Q

standard enthalpy change of neutralisation

A

enthalpy change when solutions of an acid and base react under standard conditions to produce one mole of water.
always negative as is exothermic

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11
Q

weak acid base neutralisation enthalpy

A

vary as only dissociate partially/reversibly and ions get used up quickly

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12
Q

strong acid base neutralisation enthalpy

A

no dissociation enthalpy just the reaction of H+ and OH- ions

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13
Q

pH equation

A

-log10(H+)

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14
Q

pH define

A

measure of hydrogen ion concentration

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15
Q

monoprotic acids

A

each mole of acid produces one mole of hydrogen ions

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16
Q

acid conc for strong, monoprotic acids

A

concentration of H+ ions

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17
Q

how do you find H+ conc from the pH

A

10 to the negative pH

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18
Q

polyprotic acids

A

acids with more than one proton available to release into solution.

19
Q

how do you find pH of a weak acid

A

Ka

20
Q

Ka

A

acid dissociation constant

21
Q

Ka equation

A

(H+ conc * acid conc at eq)/conc of acid at start

22
Q

Kc

A

equilibrium constant

23
Q

Kw

A

ionic product of water

24
Q

Kw equation

A

concentration of OH- * concentration of H+

25
Q

what’s Kw units

A

mol^2dm^-6

26
Q

Kw of pure water

A

conc of H+ squared

27
Q

Kw at 25 degrees celsius or 298 K

A

1*10^-14

28
Q

pKw

A

-log10(Kw)

29
Q

Kw from pKw

A

10^-pKw

30
Q

pKa

A

-log10(Ka)

31
Q

how to calibrate a pH meter

A

place in deionised water and set to 7 and repeat w standard pH solutions, washing with deionised water after every one.

32
Q

effects of diluting by a factor of 10 in strong acids

A

increases pH by 1

33
Q

effects of diluting by a factor of 10 in weak acids

A

increases pH of 0.5

34
Q

basics of how to titrate

A

measure out base with a pipette and put in a flask with an indicator.
rinse burette w acid standard solution before filling
carry out rough titration and note end point
repeat to receive concordant results (within 0.1 cm cubed of each other)

35
Q

equivalence line

A

almost vertical line on a titration curve upon which the end point lies in which all the acid has been neutralised

36
Q

methyl orange
color at low/high pH
pH of colour change

A

red at low, yellow at high

3.1-4.4

37
Q

phenolpthalein
color at low/high pH
pH of colour change

A

colourless at low
pink at high
8.3-10

38
Q

half-equivalence

A

the stage of the titration when all of the acid has been neutralised
pH at half-equivalence is actually the pKa for the acid

39
Q

buffer

A

solution that minimises change in pH when small amounts of acid or base are added.

40
Q

acidic buffer composition

A

a weak acid and a conjugate base

41
Q

how do you make acidic buffers

A

mix an excess of weak acid with a strong base

mix a weak acid with the salt of its conjugate base

42
Q

what happens when you mix excess weak acid with a strong base

A

all of the base reacts w the acid

leftover weak acid slightly dissociates

43
Q

what happens when you mix a weak acid with the salt of its conjugate base

A

salt will fully dissociate into its ions when it dissolves

ethanoic acid partially dissociates

EDEXCEL Chemistry a level (12 decks)

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