In a closed vessel at $STP$,$50 \, L$ of $CH_4$ is ignited with $750 \, L$ of air (containing $20 \% \ O_2$). The number of moles of $O_2$ remaining in the vessel on cooling to room temperature is closest to

$KMnO_4$ reacts with $KI$ in basic medium to form $I_2$ and $MnO_2$. When $250 \ mL$ of $0.1 \ M \ KI$ solution is mixed with $250 \ mL$ of $0.02 \ M \ KMnO_4$ in basic medium, what is the number of moles of $I_2$ formed?

Moles of conc. $HNO_3$ required to oxidise one mole of sulphur is :
$S + 6HNO_3 \rightarrow H_2SO_4 + 6NO_2 + 2H_2O$

What is the maximum amount of $Cl_2$ gas produced when $1 \, g$ of $HCl$ and $1 \, g$ of $MnO_2$ are heated together (in $, g$)?

Dinitrogen and dihydrogen react with each other to produce ammonia according to the following chemical equation:
$N_{2(g)} + 3H_{2(g)} \rightarrow 2NH_{3(g)}$
$(i)$ Calculate the mass of ammonia produced if $2.00 \times 10^{3} \, g$ of dinitrogen reacts with $1.00 \times 10^{3} \, g$ of dihydrogen.
$(ii)$ Will any of the two reactants remain unreacted?
$(iii)$ If yes,which one and what would be its mass?

The reactant which is entirely consumed in a reaction is known as the limiting reagent. In the reaction $2A + 4B \to 3C + 4D$,when $5 \ mol$ of $A$ react with $6 \ mol$ of $B$,then:
$(i)$ Which is the limiting reagent?
$(ii)$ Calculate the amount of $C$ formed.