In the reaction of potassium dichromate,potassium chloride and sulfuric acid (conc.),the oxidation state of the chromium in the product is $(+)$ . . . . . . .

In which compound is the oxidation state of nitrogen $+1$?

Assign the oxidation number to the underlined element in each of the following species:
$1$. $NaH_{2}\underline{P}O_{4}$
$2$. $NaH\underline{S}O_{4}$
$3$. $H_{4}\underline{P_{2}}O_{7}$

$X + Y \rightarrow$ oleum. The sum of oxidation states of the central atom in $X$ and $Y$ is:

The oxidation number of oxygen in an $O_2$ molecule is:

The oxidation number of hydrogen in $LiH$ is