pHYSICAL cHEMISTRY - II

Experiment 1

Principle

When small quantity of phenol is mixed with water and the mixture is shaken, phenol dissolves, forming a single layer. On adding larger quantities of phenol, however, two kinds of compositions (layers) of liquid are formed. The lower layer consists of small amounts of water dissolved in phenol (phenol saturated with water) and upper layer of phenol dissolved in water (water saturated with phenol).

Requirements

Chemicals: phenol in liquid state

Apparatus : Hard glass tube , Thermometer, Beakers, Stirrer, Water bath or heating mantle.

Procedure

Weigh accurately 4 gm (W1 gm) of phenol in a glass tube. (Do not touch phenol ,it is corrosive). Introduce glass rod and thermometer (with 0.1 degree centigrade accuracy) into it.

Fix the tube in a vertical position in a water bath (beaker containing water).

Set up the apparatus as shown in the Video.

Add 2 mL of distilled water to phenol and heat the test tube in a water bath, whose temperature is initially raised to about 40 degree centigrade on low flame with constant stirring.

Note the temperature (T1) of solution at which a clear and transparent solution is obtained.

It is the solution of water in phenol. Remove the tube outside the water bath and with constant stirring note the transition temperature (T2) at which turbidity reappears (this is because water separates out as a different layer).

Add 2 mL of distilled water and record the transition temperature till the temperature goes through a maximum value (CST) and comes down to about 40 degree centigrade.

Observations

Weight of phenol = W1 gm (about 4 gms)

Density of water d= 1.0 gm/mL

Observation Table

Calculations

V= mL of water added

W2 = weight of water

P = % Phenol = W1 / (W1 + W2) * 100

Graph: Plot a graph of transition temperature vs Percent by weight of phenol (P) and read the critical solution temperature. ( Maximum temperature)

Result

The critical solution temperature for phenol water system is _____ degree centigrade at ____ % by weight of phenol

Reference Material

1. Practical Physical Chemistry

2. E Journal on relevant topic.

Questions

1. State the term Critical Solution Temperature.

2. What is phase equilibrium?