<p>(a) Complete the following chemical reactions:</p>

<p>(i)&nbsp;<span class="equation">\(Na_2Cr_2O_7+KCI\to\)</span></p>

<p>(ii)&nbsp;<span class="equation">\(2MnO^-_{4} + 5SO^{2-}_3+6H^+\to\)</span>&nbsp;</p>

<p>(b) How does the colour of&nbsp;<span class="equation">\(Cr_2O^{2-}_7\)</span>&nbsp;change when treated with an alkali?</p>