Basic HTML Version
29
AVAILABLE
MARKS
Titration consistency
This is the difference between the first and second accurate readings
Difference
Mark
±0.1
[3]
±0.2
[2]
±0.3
[1]
±0.4
[0]
Titration agreement with the supervisor
Difference
Mark
±0.1
[4]
±0.2
[3]
±0.3
[2]
±0.4
[1]
±0.5
[0]
Please note that the supervisor’s titre should be recorded at the bottom of page 3
in the candidate’s script in RED INK.
The marks for table, significant figures etc should be recorded on the left-hand
side of the candidate’s table of results.
(c)
yellow to orange/red
[1]
(d)
KOH + HCl
KCl + H
2
O
[1]
(e) (i)
Correct calculation using average titre i.e.
[1]
(ii)
Use of 1:1 ratio
[1]
(iii)
Moles of potassium hydroxide 500cm
3
of diluted drain cleaner (×20) [1]
(iv)
Moles of potassium hydroxide in 25cm
3
of undiluted drain cleaner
(same value as
(iii)
)
[1]
(v)
Concentration of potassium hydroxide in drain cleaner (mol dm
-3
)
(×40)
[1]
(vi)
Concentration in mol dm
-3
(× 56)
[1]
(vii)
(gdm
-3
/1000) × 100
[1]
In part
(e)
, carry error through (c.e.t.) if appropriate.
25
titre × 0.1
1000