Question

The bottles of liquid ammonia are opened after cooling them in ice for sometime. It is because liquid ammonia:
a.) has high vapour pressure at room temperature
b.) is corrosive liquid
c.) is an explosive
d.) brings tears in eyes

Answer 1

Hint: The liquid ammonia evaporates readily when the bottle is opened and thus, it decreases in quantity. It is fact that cooling decreases the vapour pressure of the liquid. If the bottle is cooled, the ammonia remains in liquid state and does not evaporate.

Complete answer:
Liquid ammonia has high hydrogen bonding at room temperature.
So, the vapour pressure of ammonia at room temperature is very high. So, if we open the bottle then it may evaporate readily giving fumes all around. Cooling decreases the vapour pressure of the liquid. So, when the bottle is kept to cool the liquid ammonia, the vapour pressure decreases while the ammonia remains in liquid state only.
So, the bottle is cooled to decrease its vapour pressure so that the fumes do not spread around.

So, the correct answer is option a.).

Additional information:
Liquid ammonia is a colourless gas having a pungent smell. It is used as a refrigerant gas for purification of water supplies and in manufacture of plastics, pesticides, textiles and many other industrial important items.

Note:
It must be noted that if a liquid evaporates its quantity also decreases. If we leave an ammonia bottle open for some time at room temperature, then it is also possible that the complete liquid may evaporate.