<p>Give reasons for the following:</p>

<p>(i) Transition elements act as catalysts.</p>

<p>(ii) It is difficult to obtain oxidation state greater than two for copper.</p>

<p>(iii)&nbsp;<span class="equation">\(Cr_2O^{2-}_7\)</span>&nbsp;is a strong oxidising agent in acidic medium whereas&nbsp;<span class="equation">\(WO_3\)</span>&nbsp;and <span class="equation">\(MoO_3\)</span>&nbsp;are not.​​​​​​​​​​​​​​</p>