Phase Diagram of a Three Component System

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STUDENT NUMBER : 201600398

SURNAME                 : Ntlawuzana

FIRST NAME             : Ntsindiso

MODULE CODE        : SCHM321

EXPERIMENT NO.    : 2

LAB INSTRUCTOR   : Mr Zibane

DUE DATE                 : 16         March 2018

PLAGIARISM DECLARATION

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Title: Phase diagram for a three-component system

Aim: To determine the phase diagram for a three component system consisting of butanol, acetic acid and water.

Introduction

A phase diagram is coordinated triangular diagram that state the composition and relationship of three components system at constant temperature. It shows the conditions of at which thermodynamically distinct phases can occur at equilibrium (1). The number of phases of a system that can exist in equilibrium at any time depends on the conditions of temperature, concentration and composition. A three component system is represented by a triangle (2). The area within a triangle represents all the possible combinations of three components to give a three component system. When a third component is added to a pair of miscible liquid, it may affect their mutual solubility. If the third component is more soluble in one of the liquids than in the other, then the miscibility between that pair of liquids decreases (3). But, if the third component is soluble in both components, then the mutual solubility is increased. Thus, when butanol is added to a mixture of acetic acid and water, the solubility of the mixture is increased to a point where the mixture becomes homogeneous. This shows that solubility differs when different components are mixed together. The knowledge on mutual solubility can be applied in the case of preparing pharmaceutical formulation as it is often involve the mixing of more than one components while the resulting formation need to be homogeneous form. These requirements can be made possible by knowing the exact ratio of each component needed to be mixed and take into consideration the temperature and pressure of the surrounding. In this experiment, the three components were butanol, acetic acid and water. If water and acetic acid are mixed together with butanol in suitable proportion, they can form homogeneous solution at equilibrium (4). The theory behind this phenomena is that solutions are homogeneous because the ratio of solute to solvent remains the same throughout the solution even if homogenized with multiple sources, and stable because the solute will not settle it out after any period of time, and it cannot be removed by a filter paper or centrifuge (5). There are three components but only 1 phase exists.

Experimental procedure

Part 1

A volume of 20mL of water was placed in a 100mL Erlenmeyer flask. The flask was covered with a Parafilm and a burette containing 1-butanol was poked through the parafilm. Butanol was added to the water drop by drop with continuous stirring until the turbidity appeared in the mixture and remained for at least 5min. the amount of 1-butanol required was recorded. Another mixture was prepared the same way but the only difference this time was that 20mL of 1-butanol not water was placed in 100mL Parafilm-covered flask. Water was added to the 1-butanol drop by drop with continuous stirring until the turbidity appeared and remained for at least 5min. the amount of water required was recorded.

Part 2

A volume of 20mL of 1-butanol and 5mL of water were placed in a 250mL Parafilm-covered Erlenmeyer flask. Acetic acid was added drop by drop with continuous stirring until the turbidity disappeared. The volume of acetic acid was recorded. An additional 5mL of aliquot of water was further added to the mixture and again the mixture was titrated with acetic acid until turbidity disappeared. The volume of acetic added was recorded. Water was continuously added in 5mL aliquots and titrating to the turbid point with acetic acid until a total of 30mL water was added. After that a volume of 10mL aliquots was added and titrated until a total of 110mL of water was added. The volume of acetic acid was recorded at each stage.

Part 3

A volume of 25mL of water and 25mL of 1-butanol were mixed together for 5min and left to settle into two phases. A volume of 3mL of acetic acid was added and stirred again for 5min and the solution was left to settle. The solution was placed in a separating funnel and separated. The mass of each phase was determined. The bottom phase was titrated with standardized 1.0M Nao. An average of three runs was obtained. Three drops of 1% phenolphthalein solution was used as an indicator ( acidic=no color, basic=pink color, strongly basic=no color). The standardization of NaOH was done during the period that the bottom-phase titration was done since the NaOH concentration changes rapidly when carbon dioxide is absorbed from the atmosphere. A 0.25M solution of dried potassium hydrogen phthalate (KHP, M.W=204.23g/mol) for standardization and the same indicator was used for standardization.

Results

Table 1

Table 2