A-Level Chemistry Question Analysis Topic: Chemistry - Short Questions
1) Outline the principles of refining of metals by the following methods:
(i) Zone refining (ii) Vapour phase refining
2) Which aerosol depletes ozone layer?
1) (i) Zone refining applies the principle that impurities in their molten state (as opposed to their solid states) are more soluble.
A circular mobile heater is fixed at one end of an impure metal rod during the zone refining process. The molten zone of the rod moves with the heater as it moves.
As a result, the impurities move to the nearby molten zone while the pure metal crystallises out of the melt. The impurities are then segregated at one end of the rod after this procedure is carried out multiple times.
The end containing the impurities is then cut off. Materials such as silicon, boron, gallium, and indium can be purified by this method.
(ii) Vapour phase refining is when a metal is converted into its volatile compound, then decomposing it to obtain a pure metal.
There are several conditions to carrying out the process successfully:
- The volatile compound must be formed with an available reagent.
- The volatile compound should easily decompose.
Nickel, zirconium and titanium are some examples of this method.
2) The main cause of man-made chemical ozone depletion are chlorofluorocarbons and other halogenated ozone depleting substances.
Atomic chlorine is released during the breakdown of a CFC molecule. One chlorine atom can destroy over 100,000 ozone molecules. In the end, the net effect is that ozone is being destroyed more quickly than it is being produced naturally.
End of analysis. Great!