Question

Determination of b.p. of different compositions of water and ethylene glycol.

Answer 1

we know thatThe boiling point of any substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. Identify the boiling point of ethylene glycol as a boiling point of water is already known. Find what kind of mixture ethylene glycol and water is.

Complete step by step answer:
Let us know what ethylene glycol is.
Ethylene glycol which has IUPAC name of ethane-1, 2-diol. Ethylene glycol is an organic compound with the formula. It is used in many processes. It is used as a raw material in the manufacture of polyester fibres and for antifreeze formulations. Some of its physical properties are: It is an odourless, colorless, sweet-tasting, viscous liquid.
There are two ways of determination b.p. of different compositions of water and ethylene glycol.
Practical way- We will set up a 150 mL beaker on the wire gauze which is placed on a Bunsen burner. Keep the thermometer in the liquid and let it not touch the beaker.
We should heat the sample until bubbles form and record the temperature.
We will observe that the literature value for the boiling point of Ethylene glycol is 197.3 °C.
Theoretical way-
Ethylene Glycol is completely miscible in water.
First we will find the number of moles of Glycol and number of moles of water in the mixture.
From the no. of moles data we will find the molar fraction of Ethylene Glycol. From the standard tables, the vapour pressures of pure Ethylene glycol and pure water at their normal boiling points can be obtained
Use the Raoult’s law of partial pressures, to find the sum of vapour pressures
From the vapour pressure, and plot the pressure-boiling point curve for Ethylene Glycol.
We find the boiling point.

Note: Knowledge of boiling point of water is must. We should also know the literature value of ethylene glycol to compare in practical methods. The boiling point of any liquid varies with the surrounding environmental pressure. For example A liquid in a partial vacuum has a lower boiling point than when that liquid is at atmospheric pressure.