Heating of ammonium dichromate produces

The total number of $\sigma$ and $\pi$-bonds in pyrophosphoric acid are respectively

$H_4P_4O_{12}$ and $H_3P_3O_9$ have the same:

On heating with concentrated $NaOH$ solution in an inert atmosphere of $CO_{2}$,white phosphorus gives a gas. Which of the following statements is incorrect about the gas?

$P_4O_{10}$ is not used to dry $NH_3$ gas because

Cyclic polymetaphosphates have the general formula $(PO_3)_n^{n-}$. Which of the following statements is true for the cyclic trimeric metaphosphate?