Statement I In the extraction of Al by the Hall-Héroult process, pure Al2O3 mixed with Na3AlF6 lowers its melting point and increases conductivity. True. In the Hall-Héroult process, pure alumina (Al2O3) has a very high melting point (∼2050∘C). It is dissolved in molten cryolite ( Na3AlF6 ) and sometimes small quantities of CaF2 are also added. The cryolite mixture lowers the melting point to around 950−1000∘C and increases the electrical conductivity of the electrolyte. Hence, Statement I is correct. Statement II Zirconium metal is purified by zone refining method. Incorrect. The zone refining method is used for metals that need to be extremely pure and are less reactive, such as silicon, germanium, gallium, indium, etc. Zirconium (and hafnium) are purified by the van Arkel (iodide) process, not by zone refining. This process involves conversion of crude Zr into volatile ZrI4, which then decomposes on a hot filament to yield pure zirconium metal. Hence, Statement II is not correct.
