The oxidation state of $Cr$ in $CrO_5$ is

Calculate the oxidation number of $Cr$ in $CrO_4^{2-}$ ion and $K_2Cr_2O_7$ respectively.

What is the oxidation state of chlorine in chlorous acid?

When $KMnO_4$ is reduced with oxalic acid in acidic solution,the oxidation number of $Mn$ changes from

What are the oxidation numbers of the underlined elements in each of the following and how do you rationalise your results?
$(a)$ $K\underline {I_3}$
$(b)$ $H_2\underline {S_4}O_6$
$(c)$ $\underline {Fe_3}O_4$
$(d)$ $\underline {C}H_3\underline {C}H_2OH$
$(e)$ $\underline {C}H_3\underline {C}OOH$

In which of the following compounds is the maximum oxidation state of the central atom present?