Acids and Bases
Pharmaceutical Chemistry (Sem
A) (Queen Mary University of
London)
, Nam
e:
ACIDS AND BASES
Clas
s:
Time:
Marks:
Comments:
Page 1 of 142
,1 Titration curves, labelled E, F, G and H, for combinations of different aqueous
solutions of acids and bases are shown below.
All solutions have concentrations of 0.1 mol dm−3.
(a) In this part of the question, write the appropriate letter in each box.
From the curves E, F, G and H, choose the curve produced by the
addition of
(i) sodium hydroxide to 25 cm3 of ethanoic acid
(1)
(ii) ammonia to 25 cm3 hydrobromic acid
(1)
(iii) hydrochloric acid to 25 cm3 of potassium hydroxide
(1)
Page 2 of 142
, (b) The table shows information about some acid-base indicators.
Indicator pH range Lower pH colour Higher pH colour
pentamethoxy red 1.2−3.2 violet colourless
naphthyl red 3.7−5.0 red yellow
4−nitrophenol 5.6−7.0 colourless yellow
cresol purple 7.6−9.2 yellow purple
(i) Which indicator in the table could be used for the titration that produces curve E but
not for the titration that produces
curve F? Tick (✓) one box.
pentamethoxy red
naphthyl red
4−nitrophenol
cresol purple
(1)
(ii) Give the colour change at the end point of the titration that produces
curve H when naphthyl red is used as the indicator.
...............................................................................................................
(1)
(iii) A beaker contains 25 cm3 of a buffer solution at pH = 6.0
Two drops of each of the four indicators in the table are added to
this solution.
State the colour of the mixture of indicators in this buffer
solution. You should assume that the indicators do not react
with each other.
...................................................................................................
............
(1)
(Total 6 marks)
Page 3 of 142
Pharmaceutical Chemistry (Sem
A) (Queen Mary University of
London)
, Nam
e:
ACIDS AND BASES
Clas
s:
Time:
Marks:
Comments:
Page 1 of 142
,1 Titration curves, labelled E, F, G and H, for combinations of different aqueous
solutions of acids and bases are shown below.
All solutions have concentrations of 0.1 mol dm−3.
(a) In this part of the question, write the appropriate letter in each box.
From the curves E, F, G and H, choose the curve produced by the
addition of
(i) sodium hydroxide to 25 cm3 of ethanoic acid
(1)
(ii) ammonia to 25 cm3 hydrobromic acid
(1)
(iii) hydrochloric acid to 25 cm3 of potassium hydroxide
(1)
Page 2 of 142
, (b) The table shows information about some acid-base indicators.
Indicator pH range Lower pH colour Higher pH colour
pentamethoxy red 1.2−3.2 violet colourless
naphthyl red 3.7−5.0 red yellow
4−nitrophenol 5.6−7.0 colourless yellow
cresol purple 7.6−9.2 yellow purple
(i) Which indicator in the table could be used for the titration that produces curve E but
not for the titration that produces
curve F? Tick (✓) one box.
pentamethoxy red
naphthyl red
4−nitrophenol
cresol purple
(1)
(ii) Give the colour change at the end point of the titration that produces
curve H when naphthyl red is used as the indicator.
...............................................................................................................
(1)
(iii) A beaker contains 25 cm3 of a buffer solution at pH = 6.0
Two drops of each of the four indicators in the table are added to
this solution.
State the colour of the mixture of indicators in this buffer
solution. You should assume that the indicators do not react
with each other.
...................................................................................................
............
(1)
(Total 6 marks)
Page 3 of 142
