‘Lapis-Lazuli’ is a blue-coloured precious stone. It is a mineral of the class:

How can the brown color of $HNO_3$ be removed?

Which of the following is not a cyclic oxyacid?

The cyclotrimetaphosphoric acid is

Which element among the following forms $P \pi-P \pi$ multiple bonds?

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.