acids and bases

Question 1

what is an acid

Answer 1

a proton donor

Question 2

what is a base

Answer 2

a proton acceptor

Question 3

acid + bases involves what

Answer 3

the transfer of protons

Question 4

pH =

Answer 4

log [H+]
if it is Mg(OH)2 have to multiply by 2

Question 5

[H+] =

Answer 5

10^-pH

Question 6

why do you use ph scale / log scale

Answer 6

because [H+] in aqueous solution covers a wide range

Question 7

what is Kw

Answer 7

the ionic product of water

Question 8

what can you assume about H2O with kw

Answer 8

conc of H2O is very high and H2O is. effectively constant

Question 9

what is the effect of temp on ph of water

Answer 9

as temp increases equilibrium moves right to oppose the increase in temp therefor conc H+ and conc OH- increases therefore Kw increases and therefore pH decreases however the water is still neutral

Question 10

what is the definition of water

Answer 10

[H+]=[OH-]

Question 11

what is the kw you need to remember

Answer 11

Kw= 10^-14 at 298K

Question 12

what is Kw equation

Answer 12

[H+][OH-]

Question 13

what are the Ka equations

Answer 13

ka=[H+][A-]/[HA]

Ka=[H+]^2/[HA]

Question 14

pka =

Answer 14

log ka

Question 15

ka =

Answer 15

10^-pka

Question 16

what is ka dependent on

Answer 16

temperature

Question 17

in a solution of weak acid and water link [H+] and [A-]

Answer 17

[H+]=[A-]

Question 18

at equilibrium what is [H+] =

Answer 18

[HA] at initial

Question 19

what is ka

Answer 19

dissosciation constant for weak acid

Question 20

what is a buffer solution and what does it do

Answer 20

a solution where the ph doesnt change significantly when small amounts of acids or alkali is added

Question 21

what do buffers contain

Answer 21

a mixture of weak acid and weak base so the mixture can react with either acid or base, equilibria will then change in response to this change in moles

Question 22

why do acid and bases need to be weak in a buffer

Answer 22

to be in equilibrium

Question 23

what does an acidic buffer solution contain

Answer 23

a weak acid and a salt of that weak acid

Question 24

what does a basic buffer solution contain

Answer 24

a weak base and a salt of that weak base

Question 25

what does a strong acid and strong base titration curve look like

Answer 25

Question 26

what does a strong acid and weak base titration curve look like

Answer 26

Question 27

what does a weak acid and strong base titration curve look like

Answer 27

Question 28

what does a weak acid and weak base titration curve look like

Answer 28

Question 29

what is an aliquot

Answer 29

a small specific amount of volume added each time

Question 30

where is the neutralisation point on a titration graph

Answer 30

when the ph is 7

Question 31

where is the end point on a titration graph

Answer 31

when the graph ends

Question 32

where is the equivalence point on a titration graph

Answer 32

half way up the vertical part of the graph

Question 33

where do you start the curve/graph

Answer 33

at the ph of the thing that is in the conical flask e.g. if theres a strong acid in the conical flask you start the curve at ph 1/2

Question 34

how much indicator do you use

Answer 34

a small amount of indicator

Question 35

why do you use a small amount of indicator

Answer 35

as they are acids you have to use a small amounts to avoid missing the end points

Question 36

when does the indicator need to change

Answer 36

over the range of the equivalance

Question 37

why cant you choose a good indicator for weak acid and weak base

Answer 37

it changes so fast its impossible to find a good indicator

Question 38

what indicator do you use for strong acid and strong base

Answer 38

either methyl orange or phenolphthalein

Question 39

what indicator do you use for strong acid and weak base

Answer 39

methyl orange

Question 40

what indicator do you use for weak acid and strong base

Answer 40

phenolphthalein

Question 41

where is the buffer region

Answer 41

in the two horizontal bits of the graph

Question 42

where is the half equivalence point

Answer 42

when half of the equivalence point volume has been used

Question 43

what is equal at the half equivalance point

Answer 43

ph=pka

Question 44

what happens at 1/2 equivalance point

Answer 44

1/2 eq point is when in proportion 1/2 moles acid has reacted with 1/2 moles base

Question 45

what is the 1/2 eq point model answer calculation

Answer 45

[HA]=[A-] so cancel Ka= [H+][A-]/[HA] Ka= [H+] -logka = -log[H+] therefore pka = ph

Question 46

calculations : strong acid

Answer 46

([acid] to get [H+]) x number of H+ ions ----> pH = -log[H+]

Question 47

calculations : strong base

Answer 47

([base] to get [OH]) x number of H+ ions ----> kw=[H+][OH-] ----> pH = -log[H+]

Question 48

calculation : pure water in question

Answer 48

[H+]=[OH] (for pure h2o) ----> Kw= [H+]^2 ----> pH = -log[H+]

Question 49

calculation : pure weak acid in question

Answer 49

[H+]=[A-] (for pure weak acid) ----> ka=[H+]^2/[HA] ----> pH = -log[H+]

Question 50

buffer made ----> mixture of weak acid and base ----> moles of weak acid in excess ----> YES

Answer 50

OH-+HA -> A-+H20 ----> find moles of HA and A- ----> [H+] = ka[HA]/[A-] ----> ph = -log[H+]

Question 51

buffer made ----> mixture of weak acid and base ----> moles of weak acid in excess ----> NO

Answer 51

find moles of strong base left ----> do strong base method

Question 52

buffer made ----> NO mixture of weak acid and base ----> mixture of weak acid and salt

Answer 52

find moles of HA and A- ----> find [H+] from [A-]-ka([HA]/[A-]) ----> ph=-log[H+]