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

$92 \ g$ of $NO_{2(g)}$ and $32 \ g$ of $O_{2(g)}$ are taken in a rigid container. At a constant temperature,they react to produce $N_2O_{5(g)}$. The pressure in the container after the reaction is observed to be $\frac{7}{8} P$,where $P$ is the initial pressure of the gaseous mixture. The percentage yield of the reaction is ....$\%$

For the reaction $A + 2B \to C$,$5 \ mol$ of $A$ and $8 \ mol$ of $B$ will produce:

For the given reaction:
$CaCO_{3} + 2HCl \to CaCl_{2} + H_{2}O + CO_{2}$
If $90 \ g$ of $CaCO_{3}$ is added to $300 \ mL$ of $HCl$ solution which contains $38.55\%$ $HCl$ by mass and has a density of $1.13 \ g \ mL^{-1}$, then which of the following options is correct?
[Given molar masses of $H$, $Cl$, $Ca$, and $O$ are $1$, $35.5$, $40$, and $16 \ g \ mol^{-1}$ respectively]

How many moles of lead $(II)$ chloride will be formed from a reaction between $6.5 \ g$ of $PbO$ and $3.2 \ g$ of $HCl$?

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?