The document reports on an experiment to determine the enthalpy change of the neutralization reaction between sodium hydroxide and hydrochloric acid. 150 mL of 1M HCl and 50 mL of 1M NaOH were mixed in a polystyrene cup calorimeter. The temperature increase of 0.75°C was used to calculate the energy transferred of 156.75 J. Thermochemistry principles are discussed including definition of enthalpy change, methods to determine it including calorimetry, and equations used to calculate energy from temperature change measurements in solution calorimetry.

1. EXPERIMENT REPORT
OF THE ENTHALPY CHANGE OF NEUTRALIZATION
Objective:
Determine the enthalpy of sodium hydroxide with hydrochloric acid in a polystyrene
cup.
Basic of Theory:
Thermochemistry is a branch of chemistry that studies the heat of reaction involved in
a chemical reaction. As the heat of reaction is a form of energy and most chemical reactions
take place under constant pressure, the heat of reaction is then better known as enthalpy
change (ΔH).
The value of enthalpy change (ΔH) can be determined using the following three
methods:
 Experiment using calorimeter to obtain empirical enthalpy change. This method is
very useful for reactions that easily take place.
 Hess’s Law (Law of Constant Heat Summation). This method uses empirical enthalpy
change obtained from the calorimeter to determine the enthalpy change for reactions
that are difficult to study.
 Bond energy. This method uses bond energy to calculate enthalpy change. The
average bond energy values are obtained using the empirical enthalpy change data and
calculation using Hess’s Law.
A calorimeter is an apparatus used to determine the heat of reaction, thus giving the
enthalpy change value for the reaction. There are two types of calorimeter that are the simple
solution calorimeter and the bomb calorimeter. The science that studies the use of calorimeter
to measure the heat of reaction is called calorimetry.
The simple solution calorimeter is by far the easiest calorimeter to use for measuring
heat for reaction in solution. This calorimeter is made of two Styrofoam cups. As Styrofoam
is a good insulator, it can be assumed that the amount of heat absorbed/released by the
reaction is equal to the amount of heat absorbed/released by the solution. In other words, no

2. heat is absorbed/released by the system (insulated/adiabatic system). Based on this, we can
write:
qreaction + qsolution = 0
qreaction = -qsolution
qreaction = -m x c x ΔT
Where: qreaction : heat absorbed or released (J or kJ)
m : mass (g or kg)
c : specific heat (J g-1o
C-1
or J kg-1
K-1
)
ΔT : temperature change (o
C or K)
At constant pressure, the enthalpy change is the same as the heat of reaction. As the
measurement for the heat of reaction in a simple solution calorimeter is carried out at
constant pressure, and then we obtain:
ΔH = qreaction = -m x c x ΔT
The bomb calorimeter is a device that is used to measure the heat of reaction, with a
high level of accuracy. This type of calorimeter is commonly used for reactions that involve
gases, especially for combustion that takes place at high temperature and forms gaseous
substances. Basically, a bomb calorimeter consists of a sealed container, like a bomb, where
the chemical reaction takes place. The container is surrounded by water and is equipped with
a stirrer and a thermometer. To determine the heat of reaction, the sample is placed inside the
bomb including the gaseous substance that will enter via a separate valve. Once the reaction
is initiated, a transfer of heat will take place between the reaction and the calorimeter. This
will result in a change in temperature of the calorimeter (water and the other parts of
calorimeter) as indicated by the thermometer.
Let us assume that the transfer of heat only takes place between the chemical reaction
and the bomb calorimeter so that no heat from the system can get out into the surroundings
(insulated/adiabatic system). As the bomb calorimeter is composed of various components,
we will use a thermal property called the heat capacity (C) to determine the heat absorbed by
the calorimeter. So, we can write:

3. qreaction + qcalorimeter = 0
qreaction = -qcalorimeter
qreaction = -Ccalorimeter ΔT
Where: Ccalorimeter : heat capacity of calorimeter (J g-1o
C-1
or J kg-1
K-1
)
ΔT : temperature change (o
C or K)
At constant volume, the enthalpy change is approximately equal to the heat of
reaction. As the measurement for the heat of reaction in a bomb calorimeter is carried out at
constant volume, and then we obtain:
ΔH = qreaction = -Ccalorimeter x ΔT
Equipments and Materials:
Equipments:
 One unit of calorimeter
 One unit of thermometer
 One unit of Erlenmeyer flask
 One unit of beaker glass
 One unit of measuring cylinder
 One unit of pipette
 One unit of filter funnel
Materials:
 Water
 HCL

4.  NaOH
Procedures:
1. Place 150 cm3
of 1.0 mol dm-3
hydrochloric acid in the cup and record its temperature.
2. Add 50 cm3
of 1.0 mol dm-3
sodium hydroxide (at the same temperature) to the acid in
the cup.
3. Stir the reaction mixture with the temperature and record the highest temperature.
Observation data:
N
o
Experiment
Initial Temperature T1
(O
C)
Finished Temperature
T2 (O
C)
1 Solution Of Naoh 26o
C 26.5o
C
2 Solution Of HCL 26o
C 26o
C
3 Average Temperature 26o
C 26.25o
C
4 Final Temperature 27o
C 27o
C
5 Increased Temperature 1o
C 0.75o
C
Discussion:
Question and answer:
1. Calculate mole of NaOH in 50 cm3
NaOH 0.1M of solution and mole of HCL in 50
cm3
HCL 0.1M of solution.
Answer: mole NaOH= concentration x volume
1x10-1
x 5 x10-2
= 0.5 mole

5. Mole HCl= concentration x volume
1 x 10-1
x 5 x 10-2
= 0.5 mole
2. Calculate the energy transferred from the experiment!
Answer: Q = m x c x T
Q = 50 x 4.18 x 0.75
Q = 156.75 J
Conclusion:

6. Mole HCl= concentration x volume
1 x 10-1
x 5 x 10-2
= 0.5 mole
2. Calculate the energy transferred from the experiment!
Answer: Q = m x c x T
Q = 50 x 4.18 x 0.75
Q = 156.75 J
Conclusion: