1. Title :
Calculating 
Using Simple Solution Calorimeter
2. Objectives
: To calculate and determine the enthalpy
change in a reaction using simple solution calorimeter.
3.
Theory
Heat of reaction, the
amount of heat that must be added or removed during a chemical reaction in
order to keep all of the substances present at the same temperature. If the
pressure in the vessel containing the reacting system is kept at a constant value,
the measured heat of reaction also represents the change in the thermodynamic
quantity called enthalpy, or
heat content, accompanying the process—i.e., the difference between the
enthalpy of the substances present at the end of the reaction and the enthalpy
of the substances present at the start of the reaction. Thus, the heat of
reaction determined at constant pressure is also designated the enthalpy of
reaction, represented by the symbol ΔH. If the heat of reaction is
positive, the reaction is said to be endothermic; if
negative, exothermic.
The
prediction and measurement of the heat effects that accompany chemical changes
are important to the understanding and use of chemical reactions. If the vessel
containing the reacting system is so insulated that no heat flows into or out
of the system (adiabatic condition), the heat effect that accompanies the
transformation may be manifested by an increase or a decrease in temperature,
as the case may be, of the substances present. Accurate values of heats of
reactions are necessary for the proper design of equipment for use in chemical
processes.
A calorimeter
is a device used to measure the quantity of heat flow in a chemical reaction.
Two of the most common types of calorimeters are the coffee cup calorimeter and
the bomb calorimeter.
Coffee Cup Calorimeter
A coffee cup
calorimeter is essentially a polystyrene (Styrofoam) cup with a lid. The cup is
partially filled with a known volume of water and a thermometer is inserted
through the lid of the cup so that its bulb is below the water surface. When a
chemical reaction occurs in the coffee cup calorimeter, the heat of the
reaction if absorbed by the water. The change in the water temperature is used
to calculate the amount of heat that has been absorbed (used to make products,
so water temperature decreases) or evolved (lost to the water, so its
temperature increases) in the reaction.
Heat flow is
calculated using the relation:
q = (specific
heat) x m x Δt
where q is heat
flow, m is mass in grams, and Δt is the change in temperature. The specific
heat is the amount of heat required to raise the temperature of 1 gram of a
substance 1 degree Celsius. The specific heat of water is 4.18 J/(g·°C).
For example,
consider a chemical reaction which occurs in 200 grams of water with an initial
temperature of 25.0°C. The reaction is allowed to proceed in the coffee cup
calorimeter. As a result of the reaction, the temperature of the water changes
to 31.0°C. The heat flow is calculated:
qwater = 4.18
J/(g·°C) x 200 g x (31.0°C - 25.0°C)
qwater = +5.0 x
103 J
In other words,
the products of the reaction evolved 5000 J of heat, which was lost to the
water. The enthalpy change, ΔH, for the reaction is equal in magnitude but
opposite in sign to the heat flow for the water:
ΔHreaction =
-(qwater)
Recall that for an exothermic reaction, ΔH < 0; qwater
is positive. The water absorbs heat from the reaction and an increase in
temperature is seen. For an endothermic reaction, ΔH > 0; qwater is
negative. The water supplies heat for the reaction and a decrease in
temperature is seen.
4. Tools
and Materials
a.
Plastic
glass @4
b.
Plastic
glass cover @4
c.
Thermometer
d.
Stirring
rods
e.
Funnel
f.
Spatula
g.
Solution
@50 ml
i. HCl
ii. H2O
h.
Solids
@10g
i. NaOH
ii. NH4Cl
5. Procedure
a.
NaOH
+ HCl
i. Prepare a simple solution calorimeter
made from to 250 ml plastic glasses. Cover the calorimeter with a one-holed
cork for the thermometer.
ii. Take 50 ml of 0.1 M NaOH solution and 50
ml of 0.1M HCl solution. Measure the temperature of each solution. Take the
average and write it down.
iii. Pour in the NaOH solution into the
calorimeter and then add in the HCl solution. Close the calorimeter and mix the
solution carefully using the thermometer.
iv. Measure and write down the temperature.
b.
NaOH
+ H2O
i. Put 50 ml of water into 2 plastic glasses
(each 50 ml)
ii. Find the temperature of water
iii. Take 10 grams of NaOH and NH4Cl
iv. Pur NaOH to glass 1 and NH4Cl
to glass 2
v. Stir it, measure the temperature of both
solutions. When you measure it, make sure you have cleaned it before you put
into a different solution
vi. Read the temperature a moment before it
changes (up or down)
6. Data
Attached
7. Analysis
NaOH and HCl will
go into a reaction which makes the final temperature higher than the average
initial temperature. The temperature difference is 1
, thus it will result in the heat of
reaction of 
, which will result in the mole of NaOH
is 0.005 mol and the mole of HCl is 5 mol. Thus, it will have the 
reaction per mol of NaOH is 
. The theoretical enthalpy 
literature is 
, which means the % relative error is 
.
While in NaOH + H2O
reaction will increase the temperature, the initial temperature of water is 26
while the final temperature of the solution is
57
which increased by 31
, thus it is Exothermic reaction. Then NH4Cl
+ H2O reaction will decrease the temperature from 26
to
15
which decreased by 11
, thus it is Endothermic solution. In
NaOH and HCl reaction, the potential
energy of the reactant is higher than the potential energy of the product, the
energy is released, and in NaOH + H2O reaction, the potential energy
of reactant is lower than the potential energy of the product, the energy is
absorbed.
The heat of
reaction of NaOH + H2O reaction will be 
while the heat of reaction of NH4Cl
+ H2O reaction will be 
, then the mole of NaOH is 0.25 mol and
NH4Cl is 0.187 mol. Thus, the 
reaction per mol of NaOH is 
and NH4Cl is 
. The theoretical enthalpy 
literature NaOH is 
and NH4Cl is
, which means the % relative error of
NaOH is 93.8% and NH4Cl is 16.54%.
8. Conclusion
Hence, if Ti
> Tf = Endothermic, while Ti < Tf
= Exothermic. H2O will react differently toward different substance,
it can have the temperature increase, either temperature decrease. Every
substance if combined with other substance will have the reaction.
To calculate the
heat of reaction 
To find the mole
of a substance 
To find 
reaction per mol 
To find %
relative error 
Edbert Prathama / 11 Philip / 2
