Q9 / 200 · Manipal (MET) 2013 · Chemistry

If $\mathrm{CO}_2(\mathrm{~g})$ under pressure is passed into $\mathrm{Na}_2 \mathrm{CrO}_4(a q)$, yellow colour solution changes to

  • A
    blue
  • B
    green
  • C
    red
  • Correct answer
    D
    orange-red

Solution

$\begin{gathered}\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O} \rightleftharpoons \mathrm{H}_2 \mathrm{CO}_3 \rightleftharpoons \mathrm{H}^{+}+\mathrm{HCO}_3^{-} \\ \underset{\substack{2 \mathrm{CrO}_4^{2-} \\ \text { yellow }}}{2 \mathrm{Cr}^{+}} \longrightarrow \underset{\text { orange red }}{\mathrm{Cr}_2 \mathrm{O}_7^{2-}+\mathrm{H}_2 \mathrm{O}}\end{gathered}$ Aqueous $\mathrm{CO}_2$ is acidic and changes yellow $\mathrm{CrO}_4^{2-}$ into orange $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$.

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

Relevant Questions