Question

An acidified solution of potassium chromate was layered with an equal volume of amyl alcohol. When it was shaken after the addition of $1mL$ of $3\%$ ${\mathrm{H}}_2{\mathrm{O}}_2$, a blue alcohol layer was obtained. The blue color is due to the formation of a chromium $\left(VI\right)$ compound ‘$X$’. What is the number of oxygen atoms bonded to chromium through only single bonds in a molecule of $X$.

Answer 1

The reaction given can be represented as follows:

1. ${{\mathrm{CrO}}_4}^{2-}+{\mathrm{H}}_2{\mathrm{O}}_2+{\mathrm{H}}^{+}\to {\mathrm{CrO}}_5+{\mathrm{H}}_3{\mathrm{O}}^{+}$
2. Amyl alcohol act as solvent for the above reaction.
3. From the reaction it can be observed that molecule $X$ is ${\mathrm{CrO}}_5$ .
4. Structure of the compound is:
5. ${\mathrm{CrO}}_5$ has a butterfly structure.
6. $$\begin{gathered} {\mathrm{CrO}}_5\Rightarrow \mathrm{x}+5(-2)=0 \\ \mathrm{x}=+10 \end{gathered}$$
7. ${\mathrm{Cr}}^{+6}=$Maximum Oxidation state, hence proxy linkage
8. Chromium($\mathrm{VI}$) oxide peroxide(${\mathrm{CrO}}_5$) has $4$ bonds of $\mathrm{O}-\mathrm{Cr}$.