Some compounds along with their chemical formulae are given below.

Compounds	Chemical Formulae
Magnesium nitrate	$\mathrm{Mg}({\mathrm{NO}}_3{)}_2$
Aluminium nitride	$\mathrm{AlN}$
Zinc phosphate	${\mathrm{Zn}}_3({\mathrm{PO}}_4{)}_2$
Calcium oxide	$\mathrm{CaO}$

On the basis of formulae given above, the valencies or charges on ions are given below. Select the incorrect option.

Consider the following reaction,

X calcium carbonate + Y phosphoric acid $\to$ Calcium phosphate + X water + X carbon dioxide.

What is the value of X and Y?

Consider the following statements.

I. A chemical equation tells us about the substances involved in a reaction.

II. It gives information about the symbols and formula of substances involved in a reaction.

III. It tells us about the atoms or molecules of the reactants and products involved in a reaction.

The correct statement(s) is/are

Consider the following equations.

$\mathrm{Pb}\left({\mathrm{NO}}_3{)}_2\right(\mathrm{aq}) +2\mathrm{KI} (\mathrm{aq}) \to {\mathrm{Pbl}}_2(\mathrm{w}) +2{\mathrm{KNO}}_3$(x)

$\mathrm{Zn}\left(\mathrm{y}\right) +{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right) \to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right) +{\mathrm{H}}_2\left(\mathrm{z}\right)$

What are w, x, y and z in the above equations?