Experiment V05 Thermometric Titrations
Name:
Seat No.:
Chemicals:
Standard hydrochloric acid (1.0 M), (220 cm3)
Date:
sodium hydroxide solution (x M), (230 cm3)
standard ethanoic acid (1.0 M). (40 cm3)
Apparatus:
Grade:
50 cm3 measuring cylinder,
expanded polystyrene cups,(Mass = 1.78g)
thermometer (0-100 oC, in 0.1 oC graduations),
burette, pipette, glass rod.
Procedure:
A.
a.
Using a measuring cylinder, pour standard hydrochloric acid and sodium hydroxide
solution into an expanded polystyrene cup (according to the table below) and measure
the maximum temperature rise in each case.
Vol. of HCl (cm3)
0
5
10
15
20
25
30
35
40
Vol. of NaOH (cm3)
40
35
30
25
20
15
10
5
0
Max. temp. (oC)
b.
1.
Plot a graph of maximum temperature rise against the volumes of acid/alkali used.
2.
From your graph, determine the molarity of the NaOH solution.
3.
Calculate the heat of neutralization for the reaction.
Given: Specific heat capacity of solution = 4.18 J g-1 K-1
Specific heat capacity of polystyrene cup = 1.3 J g-1 K-1
P.1
Experiment V05 Thermometric Titrations
Name:
Seat No.:
Date:
B.
The experiment could be carried out by the following method alternatively:
a.
Place 25 cm3 of the NaOH solution in an expanded polystyrene cup and note the
temperature.
b.
Add HCl from a burette, in 2 cm3 portions, stir and note the highest temperature
attained by the solution. Continue adding the acid until 40 cm3 of acid have been
added.
(The experiment should be carried out quickly and each addition of acid should be
done immediately after the highest temperature of solution has noted.)
Vol. of HCl (cm3) used
0
2
4
20
22
24
6
8
10
12
14
16
18
Max. temp. (oC)
Vol. of HCl (cm3) used
26
28
30
32
34
36
38
Max. temp. (oC)
c.
1.
Plot a graph of maximum temperature rise against the volume of acid used.
2.
From your graph, determine the molarity of the NaOH solution.
3.
Calculate the heat of neutralization for the reaction.
P.2
40
Experiment V05 Thermometric Titrations
Name:
Seat No.:
Date:
C.
Using method outlined in B, find out the heat of neutralization for the reaction between
standard ethanoic acid (1.0 M) and sodium hydroxide solution (x M ). Compare the results
with that obtained from B and comment.
Vol. of ethanoic acid (cm3) used
0
2
4
20
22
24
6
8
10
12
14
16
18
Max. temp. (oC)
Vol. of ethanoic acid (cm3) used
o
Max. temp. ( C)
P.3
26
28
30
32
34
36
38 40
Experiment V05 Thermometric Titrations
Part B (Alternative method)
Time (S)
0
30
60
90
120
150
180
210
Volume (cm3)
1.00
3.90
6.80
9.80
12.70
15.60
18.20
20.80
Time (S)
240
270
300
330
360
390
420
450
23.20
25.90
28.20
30.45
32.60
34.80
36.70
38.80
Volume (cm3)
Initial Temperature: 22.6 oC
Maximum temperature: 27.1 oC
Increase in temperature(ΔT) = 27.1 oC – 22.6 oC = 4.5 oC
At equilvalent point: Time = 3.7 minutes = 222 seconds
Volume of acid used = 21.75 – 1 = 20.75 (cm3)
25
20.75
= 1×
1000
1000
20.75
M=
= 0.83 (mol dm-3)
25
M×
ΔH’= (25+20.75)×4.18×4.5 + 1.78×1.3×4.5 = 860.6 + 10.4 = 871
No. of moles of acid used = 1×0.02075 = 0.02075
871
ΔH =
= 41980 J = 41.98 kJ mol-1
0.02075
P.4