Which of the following substances are soluble in concentrated $HNO_3$?

When orthophosphoric acid is heated to $600\,^oC$,it forms .................. .

First ionisation enthalpy values of first four group $15$ elements are given below. Choose the correct value for the element that is a main component of apatite family $:$

Which oxide of nitrogen is a coloured gas?

When $NH_3$ reacts with $Cl_2$,which of the following statements are correct?
$(a)$ $NCl_3$ is formed when $Cl_2$ is in excess.
$(b)$ $N_2$ is formed when $Cl_2$ is in excess.
$(c)$ $N_2$ is formed when $NH_3$ is in excess.
$(d)$ $NCl_3$ is formed when $NH_3$ is in excess.

Which of the following is used in the industrial production of nitric acid by the Ostwald process?