The number of hydroxyl group in pyrophosphoric acid is

Write the structure of pyrophosphoric acid.

Under which conditions can active nitrogen be obtained from $N_2$ gas using an electric spark?

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?

Which oxides of nitrogen are present in significant amounts in the atmosphere?

Which element in the $N$ family (Group $15$) has the minimum ionic radius for its $M^{3-}$ ion?