Write balanced chemical equation for reaction between gold and aqua regia.

Describe the method of isolation of elemental phosphorous from ${\mathrm{Ca}}_3({\mathrm{PO}}_4{)}_2$.

Nitrous acid acts as an oxidising agent as well as reducing agent while nitric acid acts only as an oxidising agent. Support your answer with suitable examples.

How is phosphine prepared in the laboratory? Write its balanced equation. How does it react with ${\mathrm{Cl}}_2$, acidified ${\mathrm{CuSO}}_4$ solution , ${\mathrm{O}}_2$ , ${\mathrm{AgNO}}_3$ solution and $\mathrm{HI}$?

Complete the following chemical equation :

${\mathrm{Ca}}_3{\mathrm{P}}_2 \left(\mathrm{s}\right) + {\mathrm{H}}_2\mathrm{O} \left(\mathrm{l}\right) \to$

Complete the following chemical equation :

${\mathrm{P}}_{4 }+ \mathrm{NaOH} + {\mathrm{H}}_2\mathrm{O} \to$

Complete the following chemical equation :

${\mathrm{HgCl}}_2 + {\mathrm{PH}}_3 \to$