Question

Van Arkel method of purification of metals involves converting the metal to a:
A. Volatile unstable compound
B. Volatile stable compound
C. Non- volatile stable compound
D. None of the above

Answer 1

Hint: This method is related to the purification of metals, and it is also known as the crystal bar process. It is important that there should be stability in the compound after purification. We can identify the nature of compounds formed by the Van Arkel method.

Complete step by step solution:
i) First, let us know about the Van Arkel method, it was developed by Anton Eduard Van Arkel.
ii) In this method, we attain ultra-pure metals in small quantities. We can say that there is formation of metal iodides, and their decomposition occurs to yield pure metal.
iii) It is mainly used for zirconium, and titanium.
iv)Thus, it is also known as vapour phase refining. As mentioned it involves the decomposition into different substances on applying heat.
v) Thus, the iodide formed will volatize, and will start getting decomposed on filament when heated about 1800 K. Then the pure metal will be deposited on the filament.
vi) Let us take an example of nickel. As we know, nickel is reacted with carbon-monoxide at 330-350 K temperature to attain a volatile compound named as nickel tetracarbonyl.
vii) In the last, we can conclude that Van Arkel method of purification of metal involves converting the metal to a volatile stable compound.

Hence, the correct option is (B).

Note: Don’t get confused while defining this method for nickel. As this method is mainly used to remove the oxygen, and nitrogen acting as an impurity, by heating it with iodine; but it has been seen that the usage of this method is more in the purification of zirconium, and titanium.