BY
MARCIA SRI PURWANTININGSIH
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Aim
Observe the enthalpy of reaction between NaOH
solid and HCl solution with two ways.
APPRATUS /CHEMICALS
Apparatus:
Beaker Glass 250 mL
Thermometer
Materials:
NaOH solid
Hydrochloric acid 1 M
NaOH Solution 1 M
Hydrochloric acid 0.5 M
Experiment 1
NaOH(s) + H2O(l)
 NaOH
2g
50 cm3
Twater
T end
= 26
= 33
oC
oC
(aq)
NaOH(aq) +
50 cm31M
HCl (aq)  NaCl(aq) + H2O(l)
50 cm3 0,5M
50 cm3 1M 100 cm3 0,5M
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TNaOH
T HCl
T initial
T end
T end
=
=
=
=
=
27 oC
27oC
27oC
29oC
30oC
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NaOH(S) +
2g
T HCl
Tend
HCl
(aq)

NaCl(aq) + H2O(l)
100 cm3 0,5M
= 27 oC
= 38 oC
Experiment 1
Q = m . c . t
= 50 g . 4,2 j.g-1.oC-1 . 7oC
= 1442 joule
Mole NaOH = 2/ 40 = 0,05
H1 per mole
= -28840 j
= -28,84 kJ
Experiment 2
Q = m . c . t
= 100 g . 4,2 j.g-1.oC-1 . 2oC
= 840 joule
Mole NaOH = 2/ 40 = 0,05
Mole HCl = 50 ml . 0,5 M = 0,025
H2 per mole
= -33600 j
= -33,600 kJ
The other experiment
Experiment 2
Q = m . c . t
= 150 g . 4,2 j.g-1.oC-1 . 3oC
= 1890 joule
Mole NaOH = 2/ 40 = 0,05
Mole HCl = 50 ml . 0,5 M = 0,05
H2 per mole
= -37800 j
= -37,8 kJ
Experiment 3
Q = m . c . t
= 100 g . 4,2 j.g-1.oC-1 . 9oC
= 3780 joule
Mole NaOH = 2/ 40 = 0,05
Mole HCl = 100 ml . 0,5 M = 0,0 5
H3 per mole
= -75600 j
= -75,600 kJ
1.
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1. Total equation of the reaction
thermochemistry I and II (twice experiment)
H1 + H2 =
-28,84 kJ + (-33,600 kJ) = -62,44 kJ
H1 + H2 =
-28,84 kJ + (-37,8 kJ) = -66,64 kJ
2. Write the equation of the reaction thermochemistry III
H3 = -75,600 kJ
3. Whether the reaction of III equal to the total
of reactions I dan II? No, but equal reaction
and II less than reaction III
4. According to Hess law : HI + HII = HIII
Whether your data of experiment appropriate with
Hess Law?
Yes, although equal HI + HII from my
experiment less than asses HIII
5. If not, mentioned several factors cause it!
Mistake of balance sodium hydroxide solid,
because this balance is not stable, mistake of
observation, and mistake of measurement.
NaOH(S) + H2O(l) + 1/2HCl
NaOH(aq) + 1/2HCl
(aq)
(aq)
NaCl(aq) + H2O(l)
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Observation
Measure ( cylinder , balance)
Use balance
Inteprating
Reading thermometer
Accuraty
Honesty
Responsibility
Basic Competence :
2.2. Determining H of reaction based on
experiment, Hess law, standard enthalpy
change of formation and bond energies
data
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Calculating enthalpy changes of reaction
from appropriate experimental results
Calculating enthalpy change of reaction
using Standard enthalpy change of
formation data
Calculating enthalpy change of reaction
using Cycle diagram and state diagram
Calculating enthalpy change of reaction
using Bond energy