How many moles of magnesium phosphate, $\mathrm{Mg}{\left({\mathrm{PO}}_4\right)}_2$ will contain $0.25$mole of oxygen atoms? 

The mass of carbon anode consumed (giving only carbon dioxide) in the production of $270 \mathrm{kg}$ of aluminium metal from bauxite by the Hall–Héroult process:

$2{\mathrm{Al}}_2{\mathrm{O}}_3+3\mathrm{C}\to 4\mathrm{Al}+3{\mathrm{CO}}_2$

$0.01 \mathrm{mol}$ of iodoform $\left({\mathrm{CHI}}_3\right)$ reacts with $\mathrm{Ag}$ to produce a gas whose volume at $\mathrm{NTP}$ is:

$2{\mathrm{CHI}}_3+6\mathrm{Ag}\to {\mathrm{C}}_2{\mathrm{H}}_2+6\mathrm{AgI}$

The minimum quantity, in grams, of ${\mathrm{H}}_2\mathrm{S}$ needed to precipitate $63.5\mathrm{g}$ of ${\mathrm{Cu}}^{2+}$ will be nearly:

${\mathrm{Cu}}^{+2}+{\mathrm{H}}_2\mathrm{S}\to \mathrm{CuS}+{\mathrm{H}}_2$

$1.12\mathrm{mL}$ of a gas is produced at $\mathrm{STP}$ by the action of $4.12\mathrm{mg}$ of alcohol $\mathrm{ROH}$ with methyl magnesium iodide. The molecular mass of alcohol is:

$\mathrm{R}-\mathrm{OH}+{\mathrm{CH}}_3\mathrm{MgI}\to {\mathrm{CH}}_4+\mathrm{Mg}\left(\mathrm{OR}\right)\mathrm{I}$