Q66 / 180 · JIPMER 2018 · Chemistry

Among the following species, the one which become paramagnetic on heating at 850 K is

  • A
    $\mathrm{Fe}_3 \mathrm{O}_4$
  • B
    $MnO$
  • C
    $\mathrm{ZnFe}_2 \mathrm{O}_4$
  • Correct answer
    D
    Both (a) and (c)

Solution

All magnetically ordered solids, i.e. ferromagnetic; antiferromagnetic; ferrimagnetic changes to paramagnetic state at high temperature because of the randomisation of spins. Ferrimagnetic species, such as $\mathrm{Fe}_3 \mathrm{O}_4$ (magnetite) and ferrites, i.e. $\mathrm{MgFe}_2 \mathrm{O}_4$ and $\mathrm{ZnFe}_2 \mathrm{O}_4$ loses ferrimagnetism on heating and transforms to paramagnetism.

Hence, the correct answer is option: 'D'.

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