Question

A bottle of liquor ammonia should be cooled before opening. Give reason.

Answer 1

Hint: This question is based on the concept of vapour pressure. Vapour pressure is the measure of the tendency of a liquid to change into vapour or gaseous state, Vapour Pressure of any substance is a function of temperature and will decrease on cooling.

Complete solution:
As we know that liquid ammonia \[\left( {N{H_4}OH} \right)\] that is ammonia gas liquefied in water is a very much useful chemical reagent and is helpful in various chemical test and in preparation of important compounds of chemistry like nitric acid $\left( {HN{O_3}} \right)$
Due to its immense application in the field of chemistry it is present in a large amount in chemistry laboratories and industries and requires a special attention due to its high vapour pressure
Now as we all know vapour pressure determines how quickly a liquid evaporates, greater the vapour pressure of a liquid, lesser will be its boiling point and more quickly will it evaporate
Now liquid ammonia at room temperature $\left( {298K} \right)$ has a very high vapour pressure of $9.89atm$
And as soon the bottle of liquid ammonia is opened at room temperature it gets evaporated which is not good as it leads to unnecessary wastage of the substance and at the same time can cause some breathing issues and eye rashes and if it prolonged for a large duration it may lead to severe damage to eyes or even led to blindness
So to prevent these things we need to reduce the vapour pressure of liquid ammonia and it can be done by cooling it since we know that vapour pressure is a function of temperature and they both have direct relation that can be explain as follow
“On cooling liquid ammonia we decrease the temperature thus decreasing its vapour pressure which will further prevent unnecessary leakage or evaporation of the liquid ammonia to occur”.

Note: Vapour pressure is a function of temperature hence it is defined for various values of temperature like here we consider room temperature for liquid ammonia .
Always remember any changes in the temperature will always lead to changes in the vapour pressure.