What is a limiting reagent?

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 $(g \ mol^{-1}): Fe = 56, O = 16, C = 12$]

$N_{2(g)} + 3H_{2(g)} \rightleftharpoons 2NH_{3(g)}$
$20 \ g \quad \quad \quad \quad 5 \ g$
Consider the above reaction. The limiting reagent of the reaction and the number of moles of $NH_{3}$ formed are,respectively:

$8 \ L$ of $H_2$ and $6 \ L$ of $Cl_2$ react to the maximum extent. Find the final volume of the reaction mixture in $L$. Assume $P$ and $T$ remain constant throughout the process.

When $10 \, mL$ of $10 \, M \, H_2SO_4$ solution is mixed with $100 \, mL$ of $1 \, M \, NaOH$ solution,the resulting solution will be .......

According to the reaction $2A + B \to C$,$8 \ mol$ of $A$ and $5 \ mol$ of $B$ will produce how many moles of $C$?