Question

An elegant variation of Van Arkel purification method is to transport two substances in__________

(a) Same direction along the temperature gradient

(b) Opposite direction along the temperature gradient

(c) Same direction along the concentration gradient

(d) Opposite direction along the concentration gradient

I got this question in an interview for job.

The origin of the question is Crystallization of Solutions, Melts, Glasses and Gels in chapter Preparative Methods of Solid State Chemistry

Answer 1

The correct answer is (b) Opposite direction along the temperature gradient

For explanation I would say: Van Arkel method is a purification method which uses metal and iodine to form gaseous iodide, it transports two substances in opposite directions along the temperature gradient and this is possible when one reaction is exothermic and the other is endothermic.