Which of the follwing are main requirements for vapour phase refining ?
(i) Metal should form a volatile compound with the reagent
(ii) The volatile compound should be easily decompsoable to give back pure metal
(iii)Metal should be very reactive and form a stable compound with the reagent

Options

A. (i), (ii) and (iii)
B. (i) and (ii)
C. (ii) and (iii)
D. (i) and (iii)

Answer

To determine the main requirements for vapor phase refining, we need to evaluate the given statements one by one:

1. **Metal should form a volatile compound with the reagent.**
- This statement is true. For vapor phase refining to occur, the metal must be able to react with a reagent to form a volatile compound. This is essential because the process relies on the volatility of the compound to separate the metal from impurities.

2. **The volatile compound should be easily decomposable to give back pure metal.**
- This statement is also true. After forming the volatile compound, it must be capable of being decomposed easily to yield the pure metal. This is a critical step in the vapor phase refining process.

3. **Metal should be very reactive and form a stable compound with the reagent.**
- This statement is not necessarily a requirement for vapor phase refining. While reactivity can be beneficial, it is not a strict requirement. The key requirement is that the metal forms a volatile compound that can be decomposed, rather than being very reactive and forming a stable compound.

Based on the evaluation of these statements, we can conclude:
- Statements 1 and 2 are correct.
- Statement 3 is not a requirement.

Thus, the correct answer is **Option B: 1 and 2**.