Refining

Step 1: Understanding the van-Arkel method.
The van-Arkel method is used for the purification of metals by converting the metal into a volatile compound, which can then be decomposed to obtain pure metal.

Step 2: Explanation of the options.
- (1) Volatile stable compound: This is the correct option. In the van-Arkel method, the metal is first converted into a volatile stable compound.
- (2) Non-volatile stable compound: This is not the method used in van-Arkel's purification technique.
- (3) Volatile unstable compound: While volatility is involved, the compound is stable and not unstable.
- (4) None of the above: This option is incorrect as option (1) is the correct answer.

Step 3: Conclusion.
The correct answer is (1) Volatile stable compound.

Step 1: Formula / Definition}

Step 2: Calculation / Simplification}
Unsymmetrical epoxide opening follows at less hindered carbon.
attacks terminal carbon.
Ring opens forming alkoxide on secondary carbon.
Protonation yields (Propan-2-ol).
Step 3: Final Answer

Concept:
• Mond’s process refining of nickel using volatile
• Van Arkel method refining of titanium and zirconium using iodide process

Step 1: Identify metals.
Mond’s Nickel
Van Arkel Titanium (also Zr)

Step 2: Match option.
Correct pair: Nickel, Titanium