TITLE:
Determination of phase diagram for ethanol/ toluene/ water system theory
OBJECTIVES
: To
determine the phase diagram for ethanol / toluene / water system
DATE
OF EXPERIMENT: 04/11/2014 (Tuesday)
INTRODUCTION
:
Ternary systems are
those having three components. In this experiment, we investigate the behavior
of a system of three liquids: ethanol, toluene and water. Water is insoluble
with toluene, but as it were mixed together with ethanol, a homogenous solution
will be formed, provided that correct proportion is used when mixing all these
three types of solution together. Therefore, in this system, we can see that
only one phase exists although there are three components.
According to the phase
rule, a single phase in a three-component system may posses four degrees of
freedom that are temperature, pressure, and concentrations of the two of the
three components.
F = C – P + 2
= 3
– 1 + 2
= 4
Figure 1 : Ternary
Phase Diagram
Based
on the diagram above, each peak of the triangle diagram represents 100% of
different component respectively. Each side of the triangle represents a binary
mixture where two components mixed together and any line drawn parallel to one
of the sides shows the percentage of a particular component. For example, line
DE means there are 20% of A. At intercept point K, there are combination of 20%
of A, 50% of B and 40% of C.
APPARATUS
:
·
Burette
·
Conical flask
·
Retort stand and clamp
·
Measuring cylinder
·
Test tubes
CHEMICALS
:
·
Ethanol
·
Toluene
·
Distilled water
PROCEDURES:
1. Mixtures of ethanol and toluene were prepared in sealed
containers measuring 100cmᵌ containing the following percentages of ethanol:
10%, 25%, 35%, 50%, 65%, 75%, 90%, 95%.
2. 20ml of each mixture is prepared by filling a certain volume
using burette.
3. Each mixture is titrated with water until cloudiness is
observed due to the existemce of a second phase.
Doing titration to add water into the
conical flask containing mixture of toluene and ethanol.
4. A little water was added and shaken well after each addition.
5. The room temperature was measured using the thermometer.
6. The percentage based on the volume of each component was
calculated when the second phase starts to appear.
7. The points were plotted onto a triangular paper to give a
triple phase diagram at the recorded temperature.
8. Few more measurements can be done if necessary.
RESULTS:
|
Percentage
of ethanol ( % )
|
10
|
25
|
35
|
50
|
65
|
75
|
90
|
95
|
|
Volume
of ethanol (mL)
|
2
|
5
|
7
|
10
|
13
|
15
|
18
|
19
|
|
Volume
of toluene (mL)
|
18
|
15
|
13
|
10
|
7
|
5
|
2
|
1
|
|
Volume
of water (i) (mL)
|
0.30
|
0.60
|
0.80
|
1.50
|
3.40
|
5.60
|
10.80
|
16.2
|
|
Volume
of water (ii) (mL)
|
0.20
|
0.40
|
1.00
|
1.40
|
3.00
|
5.20
|
11.20
|
16.0
|
|
Average
volume of water (mL)
|
0.25
|
0.50
|
0.90
|
1.45
|
3.20
|
5.40
|
11.00
|
16.10
|
CALCULATION
:
|
Component
/ Percentage (%)
|
|
|
|
|
|
|
|
|
|
Ethanol
|
9.88
|
24.39
|
33.49
|
46.62
|
56.03
|
59.05
|
58.06
|
52.63
|
|
Toluene
|
88.89
|
73.17
|
62.20
|
46.62
|
30.17
|
19.69
|
6.45
|
2.77
|
|
Water
|
1.23
|
2.44
|
4.31
|
6.75
|
13.79
|
21.26
|
35.48
|
44.60
|
DISCUSSION:
Ternary phase diagram are the diagram that
containing three component which are ethanol, toluene and water. This type of
diagram is three-dimensional but is illustrated in two-dimensions for ease of
drawing and reading. Each peak of the triangular diagram is 100% of one
component by weight (Ethanol, Toluene or Water). In the other hand, the same
peak is also the 0% of the other two component by weight. The result shows that
when the ethanol added increases, the volume of water needed to turn the
mixture into cloudy will also increases. Mixture turns cloudy due to the
existence of second phase. When water is added into the mixture of ethanol and
toluene, the mixture turns cloudy because water is more soluble in ethanol than
in toluene. When the third component added into the mixture is more soluble in
one of the component of the duo, it will decrease the mutual solubility of the
mixture and second phase will be shown like what is observed in this
experiment. However, when more water is added until it reach an appropriate
amount, it will result to one phase system where homogenous solution is formed
at this point.
During conducting this experiment, some
errors have occurred. Firstly, the degree of cloudiness is confusing when there
is different range of cloudiness among different people who was conducting this
experiment. This is because there is no a specific range for the degree of
cloudiness which will causes inaccurate amount of water added into the mixture.
Therefore, the degree of cloudiness for each mixture must be consistent every
time to prevent any result deviation. Besides, eye level not perpendicular to
the scale of the measuring cylinder when measuring the volume of the toluene
and ethanol. Inaccurate reading will be mistakenly recorded. Therefore, eyes
level of the observer must be perpendicular to the reading scale to avoid
parallax error.
Furthermore, errors occurred during
conducting this experiment included pouring mixture of toluene and ethanol into
the conical flask which containing water droplets. This will affect the
experiment result, thus should be prevented by making sure every conical flasks
are fully dried before pouring the mixture inside. In addition, the mixture
should be shaken gently and the rate of agitation must be constant so that it
will not affect the volume of water added into the mixture. For every drop of
water added, the conical flask containing the mixture must be shaken well.
QUESTIONS
1. Does the mixture containing 70%
ethanol, 20% water and 10% toluene (volume) appear clear or does it form two
layers?
Clear solution will appear.
2. What will happen if you dilute 1
part of the mixture with 4 parts of
a)
Water
The solution will appear in two layers because
two phases will be formed.
b)
Toluene
The solution will appear in two layers because
two phases will be formed.
c)
Ethanol
The
solution will appear in one layer because there is only one phase formed.
CONCLUSION
This experiment shows
us that three component system is a condensed system. The solution will appear
in two phase, where a part is rich in water and the other part is rich in
toluene when the solution is not completely miscible. Ethanol, toluene and
water is a ternary system with one pair of partially soluble liquid that is
toluene and water.
REFERENCES
1.
Martin, A.N. – Physical and
Pharmaceutical Pharmacy, Sixth Edition: Physical Chemistry Principles in
Pharmaceutical Sciences
3. http://chemwiki.ucdavis.edu/Physical_Chemistry/Physical_Properties_of_Matter/Phase_Transitions/Phase_Diagrams
4.
http://www.brocku.ca/earthsciences/people/gfinn/petrology/ternary3.htm
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