<p>When chromite ore&nbsp;<span class="equation">\(FeCr_2O_4\)</span>&nbsp;is fused with NaOH in presence of air, a yellow coloured compound (A) is obtained which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCI forms an orange coloured crystalline compound (C).</p>

<p>(i) Write the formulae of the compounds (A), (B) and (C)</p>

<p>(ii) Write one use of compound (C)</p>