To an acidified dichromate solution, a pinch of Na₂O₂ is added and shaken. What is observed?

$C{r}_2{O}_7^{2-}+10H^{+}+4N{a}_2{O}_2\to \underset{bluecolour}{Cr{O}_5}+8N{a}^{+}+5H_{2}O$ 
In absence of  ether, $Cr{O}_5$   decomposes  to $C{r}^{3+}$  with the evolution of  $O_2$
$4Cr{O}_5+12H^{+}\to \underset{green}{4C{r}^{3+}}+7O_2+6H_{2}O$