What is the oxidation number of carbon in $CH_2O$?

What is the oxidation state of $Fe$ in $Fe_{0.94}O$?

If $HNO_3$ changes into $N_2O$,the oxidation number of nitrogen is changed by

One mole of $N_2H_4$ loses $10 \ moles$ of electrons to form a new compound $Z$. Assuming that all the nitrogen atoms appear in the new compound,what is the oxidation state of nitrogen in $Z$? (There is no change in the oxidation state of hydrogen.)

When $K_2Cr_2O_7$ is converted to $K_2CrO_4$,the change in the oxidation state of chromium is

The average oxidation state of sulphur in $Na_2S_2O_3$ is: