Question

For oxidizing alcohols, several oxidants – each with a multivalent central atom as the active species – can be used. When Chromic acid, with Cr as the multivalent atom is used, how many bonds to oxygen atoms does each central multivalent atom have just before and immediately after the oxidation respectively?

• A. 7 - before,5 -after
• B. 7 – before, 4 – after
• C. 6 – before, 4 – after
• D. 6 – before, 3 – after

Answer 1

The correct option is C

6 – before, 4 – after

Chromium exists in the +6 oxidation state in $H_{2}Cr{O}_4$.
After, reduction, it becomes $H_{2}Cr{O}_3$ before getting converted into $C{r}^{3+}$ all the way.

As shown above, there are 6 bonds 9Cr has with oxygen) before the reaction and 4 after (below).