In which oxidation state, group 15 elements act as Lewis base?

Relationship between van't Hoff's factor (i) and degree of dissociation $(\alpha)$ is

Which of following elements does not react with hot concentrated sulphuric acid?

In the reaction, $\mathrm{H}_2 \mathrm{O}_2(a q) \xrightarrow{\mathrm{I_{(aq)}^-}} \mathrm{H}_2 \mathrm{O}(I)+\frac{1}{2} \mathrm{O}_2(g)$ iodide ion acts as