(i) Name the common refrigerant. How does it deplete ozone layer?

(ii) What is the alternative of chlorofluorocarbon carbon?

(iii) State the advantages and disadvantages of using ammonia as refrigerant?

(i) The main refrigerants used are Freon chlorofluorocarbons (CFC). They deplete ozone layer and contribute to global warming. The chlorofluorocarbons are decomposed by ultraviolet rays to highly reactive chlorine which is produced in the atomic form.

$\text{CF}$2\text{Cl}2 \xrightarrow{\text{Ultraviolet}} \text{CF}_2\text{Cl} + \text{Cl} [\text{free radical}]

The free radical [Cl] reacts with ozone and chlorine monoxide is formed.

Cl + O₃ [ozone] ⟶ ClO + O₂

This causes depletion of ozone. Chlorine monoxide further reacts with atomic oxygen and produces more free radicals.

ClO + O ⟶ Cl + O₂

Again this free radical [Cl] destroys ozone, and the process continues thereby giving rise to ozone depletion.

(ii) Liquid ammonia

(iii) Advantages of ammonia as refrigerant:

1. Ammonia is environmentally compatible. It does not deplete ozone layer and does not contribute towards global warming.
2. It has superior thermodynamic qualities as result ammonia refrigeration systems use less electricity.
3. Ammonia has a recognizable odour and so leaks are not likely to escape. It being lighter than air goes up in the atmosphere not affecting the life too much on earth.

Disadvantages of ammonia as a refrigerant are as follows:

1. It is not compatible with copper, so it cannot be used in any system with copper pipes.
2. It is poisonous in high concentration.