Question

Define the following terms. Give an example of the relevance of the term in an industrial setting. i.Boiling Point:

ii. Vapor Pressure:

iii. Lower Explosive Limit:

iv. Upper Explosive Limit:

v. Rate of Evaporation:

Answer 1

(1) Boiling point is defined as the temperature at which the vapour pressure of the given liquid equals the pressure surrounding the liquid, where the liquid changes to vapour. Eg: In industrial setting boiling point is used in the terms of distillation, where the mixture of components will get separated by the evapaoration and condensation. Using distillation liquid mixtures are separated physically. In industry large amounts of crude liquids such as gasolene are separated and purified using distillation. Also the Salt water is converted to fresh water using distillation.

(2)Vapor pressure : In a closed system the pressure which is exerted by the vapor stabilises and equals the rates of evaporation and condensation is termed as vapor pressure. Eg: Volatile liquids which have higher boiling points have high vapor pressures and non volatile liquids have low vapor pressures.

(3)Lower Explosive limit(LEL) : Also known as lower flammable limit. It is defined as the lower concentration of vapour or gases present which are able to produce a spark of fire in the flammable environment such as heat. below this limit the gases or the vapour are too lean to burn. Eg: LEL of acetone is 2.6, ammonia is 15.0, cyclohexane is 1.3

(4) Upper Explosive limit (UEL): Also known as upper flammable limit which is defined as the high concentrations of gases present which would produce spark in the presence of flmmable environment. gaes having high cocentrations than UEL are too rich to burn. Eg: UEL of acetone is 13.0, ammonia is 28.0, cyclohexane is 7.8

(5) Rate of Evaporation: It is defined as the rate at which the liquid vapourises in comparision to the vaporisation rate of the known susbstance. it is an important factor which depends on temperature, surface area etc,substances which ahve high rate of evaportion can be explosive.Eg: Hexane, methyl ethyl ketone, acetone are known to have fast evaportion rates.