The mass of water produced when $4 \ g$ of hydrogen reacts with $4 \ g$ of oxygen is .......... $g$.

Production of iron in a blast furnace follows the following equation:
$Fe_{3}O_{4(s)} + 4CO_{(g)} \rightarrow 3Fe_{(s)} + 4CO_{2(g)}$
When $4.640 \ kg$ of $Fe_{3}O_{4}$ and $2.520 \ kg$ of $CO$ are allowed to react,the amount of iron (in $g$) produced is $....$
[Given: Molar Atomic mass $(g \ mol^{-1}): Fe = 56, O = 16, C = 12$]

What is the number of moles of water molecules required to prepare $n$ moles of methane from $n$ moles of methyl magnesium iodide?

In a reaction $A + B_2 \rightarrow AB_2$,identify the limiting reagent,if any,in the following reaction mixtures:
$(i)$ $300$ atoms of $A + 200$ molecules of $B_2$
$(ii)$ $2 \ mol \ A + 3 \ mol \ B_2$
$(iii)$ $100$ atoms of $A + 100$ molecules of $B_2$
$(iv)$ $5 \ mol \ A + 2.5 \ mol \ B_2$
$(v)$ $2.5 \ mol \ A + 5 \ mol \ B_2$

For the reaction,$2Fe(NO_3)_3 + 3Na_2CO_3 \to Fe_2(CO_3)_3 + 6NaNO_3$. Initially,if $2.5 \ mol$ of $Fe(NO_3)_3$ and $3.6 \ mol$ of $Na_2CO_3$ are taken. If $6.3 \ mol$ of $NaNO_3$ is obtained,then the $\%$ yield of the given reaction is:

$100 \ mL$ of $0.05 \ M$ $Cu^{2+}$ aqueous solution is added to $1 \ L$ of $0.1 \ M$ $KI$ solution. The number of moles of $I_2$ and $Cu_2I_2$ formed are respectively: