What is the basicity of orthophosphoric acid?

Which of the following statements are correct about the reaction between the copper metal and dilute $HNO_3$?
$(I)$ The principal reducing product is $NO$ gas.
$(II)$ $Cu$ metal is oxidised to $Cu^{2+}$ (aq.) ion which is blue in colour.
$(III)$ $NO$ is paramagnetic and has one unpaired electron in antibonding molecular orbital.
$(IV)$ $NO$ reacts with $O_2$ to produce $NO_2$ which is linear in shape.
Choose the correct statements.

Which of the following reactions correctly represent the products formed upon heating?
$(a) \ NH_4NO_2 \xrightarrow{\Delta } N_2 + 2H_2O$
$(b) \ NH_4NO_3 \xrightarrow{\Delta } N_2O + 2H_2O$
$(c) \ Na_2CO_3 \xrightarrow{\Delta } Na_2O + CO_2$
$(d) \ NH_4Cl \xrightarrow{\Delta } NH_3 + HCl$

$PCl_{5} + P_{4}O_{10} \xrightarrow{\Delta } X$. The product $(X)$ is an oxygen-containing compound. How many moles of an oxyacid are formed on the complete hydrolysis of $1 \text{ mole}$ of $(X)$?

Which of the following oxyacids contains both $P-H$ and $P-P$ bonds simultaneously?

Which of the following is formed when aluminium oxide and carbon are strongly heated in dry chlorine gas?