TITLE :
Determination
of Phase Diagram for Ethanol/Toluene/Water System Theory
(Three-Component Systems)
OBJECTIVE :
To
identify the miscibility of the mixtures of three components which are Ethanol,
Toluene and Water.
DATE OF EXPERIMENT :
7
November 2016
INTRODUCTION :
Figure
above is known as the triangular or ternary phase diagram at which three
components are involved in a system. The phase diagram states the
coordinate of compositions of the three components with temperature
and pressure as the fixed variables. Each apex of the triangle: A, B
and C represents 100% pure for a component and the same apex will
represent 0% for other two components. Meanwhile, each side of the
triangle represents two-component mixtures such that side AB contains
only mixture of A and B and so on while the area within the triangle
itself consists of the three-component system. Any line parallel to a
side of the triangular phase diagram shows constant percentage of a
component. For example, any point lies on the line CD in the
figure above shows constant percentage of 30% B with varying
composition of A and C.
The
addition of third component to a pair of miscbile liquids can change
their mutual solubility such that the third component may increase or
decrease the mutual solubility. Further increasing the mutual
solubility of the liquid pair may result in what we called homogenous
mixture, a single-phase system where three liquids are miscible
together. Thus, the determination of compositions for each component
by using triangular phase diagram is important.
APPARATUS :
Measuring
cylinder, beaker, burette, conical flask, retort stand and clamp.
MATERIALS :
Ethanol,
toluene and distilled water.
PROCEDURE :
1.
20 mL mixtures of ethanol and toluene containing the following
percentages of ethanol are prepared. (10%, 25%, 35%, 50%, 65%, 75%,
90% and 95% of ethanol)
2.
Each mixture is then titrated with water until cloudiness is observed
due to the existence of second phase. Little water is added and the
mixture is shaken well after each addition.
3.
The room temperature is recorded.
4.
The percentage based on the volume of each component when the second
phase starts to appear is calculated.
5.
Points of percentage are plotted onto a triangular paper to give a
triple phase diagram at the recorded temperature.
6.
The experiment is repeated and the average volume is calculated.
DISCUSSION :
Based on the experiment, ternary phase diagram contains three component which are water, ethanol and toluence. A phase diagram shows the phase existing in equilibrium at any given condition. According to the phase rule, a maximum of four intensive variables such as pressure, temperature and the concentration of two of the three component must be specified to completely defined the state of a three component. In systems containing three component may possess four degrees of freedom.
A
simplification is achieved by choosing one of the intensive variables
as a parameter in this experiment. If concentration is chosen as a
parameter the condition of equilibrium can be represented by using a
triangular prisms each corresponding to a different concentration
that shown in the diagram above.This
graph accounts for the fact that only two variables are
required.Along the phase boundary only one variable is required.
From the diagram, each corner represent 100% of ethanol, 100% of toluence and 100% of water while other two component are 0%. YZ line represent the water-toluence system, YX line represent water-ethanol system and XZ line represent ethanol-toluence system.In going along a line bounding the triangle so as to represent the concentration in two-component system, it does not matter whether we proceed in clockwise or counterclockwise direction around the triangle. The more usual convention is clockwise and has been adopted here.Hence, as we move along YX in the direction of X we are signifying system of water and ethanol containing increasing of ethanol and correspondingly the smaller amount of water.Moving along the XZ toward Z will represent system of X and Z. At the same time, the concentration of ethanol are decreasing toward the Z system while concentration of toluence is higher. The closer we approach toluence on the line of YZ, the greater will be the concentration of water in system of Y and Z.The area within the triangle represent all the possible combination of water, ethanol and toluence to give three component system.For example, the conical flask A, the system consist of 6.32% of water, 84.31% of toluence and 9.37% of ethanol.If a line is drawn through any apex to a point on the opposite side, then all the systems represented by points on such a line have a constant ratio of two components. Any line drawn parallel to one side of the triangle represent ternary system in which the proportion (or precent by weight)of one component is constant . The curve of the plotted graph is termed as binomial curve. The region bounded by the curve shows the presence of two phases. The mixture within this region is cloudy in appearance due to phase separation as amount of ethanol are not sufficient for a homogenous solution.
Based
on the result obtained, when there is a higher percentage of ethanol
compared to percentage of toluence in the mixture, the volume of
water needed to titrate the mixture until cloudiness is observed is
higher. This proves that the ethanol has increased the miscibility of
the other two component and more water is needed to break
homogeneity.
There
are some errors made during the experiment. One of the errors is due
to the degree of cloudiness. Different person did the observation
each time will cause the different degree of cloudiness of mixture
achieved. Another error is parallax error. Our
eyes must be perpendicular to the scale of measurement. This cause
inaccurate measurement of liquid. Ethanol and toluence are very
volatile liquids. Their volume may be less than actual needed value
as some of them have been evaporated. Avoid expose ethanol and
toluence with air for too long. This is because to prevent it
vaporize to the surrounding. The contaminated apparatus may affect
the result as well. The glass wares were not completely dried after
washing will cause slight dilution of the mixture. rinse the the
glassware before use to remove impurities as the impurities may
affect the result.
QUESTIONS & ANSWERS :
Toluene : 0.1 + 4 / 1 + 4 x 100 = 82%
Water : 0.2 / 1 + 4 x 100 = 4%
RESULTS :
%
of ethanol
(v/v)
|
Volume
of ethanol (mL)
|
Volume
of toluene (mL)
|
Titration
of water I (mL)
|
Titration
of water II (mL)
|
Average
titration (mL)
|
10
|
2
|
18
|
1.7
|
1.0
|
1.35
|
25
|
5
|
15
|
0.7
|
1.0
|
0.85
|
35
|
7
|
13
|
0.7
|
0.7
|
0.70
|
50
|
10
|
10
|
1.4
|
1.3
|
1.35
|
65
|
13
|
7
|
2.5
|
2.3
|
2.40
|
75
|
15
|
5
|
4.5
|
4.2
|
4.35
|
90
|
18
|
2
|
10.4
|
10.9
|
10.65
|
95
|
19
|
1
|
16.1
|
22.9
|
19.50
|
Total
volume of mixture (mL)
|
Composition
of Ethanol
|
Composition
of Toluene
|
Composition
of Water
|
|||
Volume
(mL)
|
%
|
Volume
(mL)
|
%
|
Volume
(mL)
|
%
|
|
21.35
|
2
|
9.37
|
18
|
84.31
|
1.35
|
6.32
|
20.85
|
5
|
23.98
|
15
|
71.94
|
0.85
|
4.08
|
20.7
|
7
|
33.82
|
13
|
62.80
|
0.70
|
3.38
|
21.35
|
10
|
46.84
|
10
|
46.84
|
1.35
|
6.32
|
22.4
|
13
|
58.04
|
7
|
31.25
|
2.40
|
10.71
|
24.35
|
15
|
61.61
|
5
|
20.53
|
4.35
|
17.86
|
30.65
|
18
|
58.72
|
2
|
6.53
|
10.65
|
34.75
|
39.5
|
19
|
48.10
|
1
|
2.53
|
19.50
|
49.37
|
DISCUSSION :
Based on the experiment, ternary phase diagram contains three component which are water, ethanol and toluence. A phase diagram shows the phase existing in equilibrium at any given condition. According to the phase rule, a maximum of four intensive variables such as pressure, temperature and the concentration of two of the three component must be specified to completely defined the state of a three component. In systems containing three component may possess four degrees of freedom.
F=C-P+2
=3-1+2
=4
F=
degree of freedom, C= component, P= phase
From the diagram, each corner represent 100% of ethanol, 100% of toluence and 100% of water while other two component are 0%. YZ line represent the water-toluence system, YX line represent water-ethanol system and XZ line represent ethanol-toluence system.In going along a line bounding the triangle so as to represent the concentration in two-component system, it does not matter whether we proceed in clockwise or counterclockwise direction around the triangle. The more usual convention is clockwise and has been adopted here.Hence, as we move along YX in the direction of X we are signifying system of water and ethanol containing increasing of ethanol and correspondingly the smaller amount of water.Moving along the XZ toward Z will represent system of X and Z. At the same time, the concentration of ethanol are decreasing toward the Z system while concentration of toluence is higher. The closer we approach toluence on the line of YZ, the greater will be the concentration of water in system of Y and Z.The area within the triangle represent all the possible combination of water, ethanol and toluence to give three component system.For example, the conical flask A, the system consist of 6.32% of water, 84.31% of toluence and 9.37% of ethanol.If a line is drawn through any apex to a point on the opposite side, then all the systems represented by points on such a line have a constant ratio of two components. Any line drawn parallel to one side of the triangle represent ternary system in which the proportion (or precent by weight)of one component is constant . The curve of the plotted graph is termed as binomial curve. The region bounded by the curve shows the presence of two phases. The mixture within this region is cloudy in appearance due to phase separation as amount of ethanol are not sufficient for a homogenous solution.
QUESTIONS & ANSWERS :
Questions & Answers
1.
Does the mixture containing
70% ethanol, 20% water and 10% toluene (volume) appear clear or does it form
two layers?
-
The mixture appears clear
which is one liquid phase.
2.
What will happen if you
dilute 1 part of the mixture with 4 parts of (a) water (b) toluene (c) ethanol?
-
Water : 20/100 x 1 = 0.2
-
Toluene : 10/100 x 1 = 0.1
Ethanol
: 0.7 / 1 + 4 x 100 = 14%
Water : 0.2 +4 / 1 + 4 x 100 = 84%
Toluene : 0.1 / 1 + 4 x 100 = 2%
-
Two liquid phase will
form and mixture become cloudy.
(b) Add 4 parts of toluene
Ethanol : 0.7 / 1 + 4 x 100 = 14%
Water : 0.2 / 1 + 4 x 100 = 4%
-
A single liquid phase
is formed.
(c) Add 4 parts of ethanol
Ethanol : 0.7 + 4 / 1 + 4 x 100 = 94%
Toluene : 0.1 / 1 + 4 x 100 = 2%
-
A clear single liquid
phase is formed.
In conclusion, ethanol,toluence and water system is a ternary system
with one pair of partially miscible( toluence and water). The
addition of sufficient amount of ethanol to the toluence water-system
would produce a single liquid phase in which all the three component
are miscible and the mixture is homogenous. As the number of volume
of ethanol by percentage increase and number of volume of toluence by
percentage decrease, the volume of water will increase. The two phase
system only shown if the water added exceed the theoritical
percentage where the three component are partially miscible. Data
also show that when percentage of toluence is higher compared to
ethanol, only small amount of water needed to break the homogenity.
REFERENCES :
1. Alexander T.& David A., 2006, Physicochemical Principles of Pharmacy Fourth Edition [pg. 221], Pharmaceutical Press, London, USA.
2. Ternary Phase Diagrams, retrieved from https://brocku.ca/earthsciences/people/gfinn/petrology/ternary2.htm
3. 2012, Ternary Phase Diagrams, ASM International, retrieved from http://www.asminternational.org/documents/10192/1849770/05342G_Sample_BuyNow.pdf/230f1568-32a2-4669-a03d-b33278ca8825
REFERENCES :
1. Alexander T.& David A., 2006, Physicochemical Principles of Pharmacy Fourth Edition [pg. 221], Pharmaceutical Press, London, USA.
2. Ternary Phase Diagrams, retrieved from https://brocku.ca/earthsciences/people/gfinn/petrology/ternary2.htm
3. 2012, Ternary Phase Diagrams, ASM International, retrieved from http://www.asminternational.org/documents/10192/1849770/05342G_Sample_BuyNow.pdf/230f1568-32a2-4669-a03d-b33278ca8825
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