If $30 \, mL$ of $H_2$ and $20 \, mL$ of $O_2$ react to form water,what remains at the end?

If $0.5 \ mol$ of $CaBr_2$ is mixed with $0.2 \ mol$ of $K_3PO_4$,then the maximum number of moles of $Ca_3(PO_4)_2$ obtained will be:

Under similar conditions of pressure and temperature,$40 \, mL$ of slightly moist hydrogen chloride gas is mixed with $20 \, mL$ of ammonia gas,the final volume of gas at the same temperature and pressure will be ............. $mL$.

Calculate the amount of carbon dioxide that could be produced when
$(i)$ $1$ mole of carbon is burnt in air.
$(ii)$ $1$ mole of carbon is burnt in $16 \ g$ of dioxygen.
$(iii)$ $2$ moles of carbon are burnt in $16 \ g$ of dioxygen.

The mass of $Mg_3N_2$ produced if $48 \ g$ of $Mg$ metal is reacted with $34 \ g$ $NH_3$ gas is:
$3Mg + 2NH_3 \to Mg_3N_2 + 3H_2$

$A$ closed $10 \, L$ vessel contains $1 \, L$ water gas $(1:1 \, CO : H_2)$ and $9 \, L$ air ($20 \% \, O_2$ by volume) at $STP$. The contents of the vessel are ignited. The number of moles of $CO_2$ in the vessel is closest to $.... \, mol$.