$250 \ mL$ of $0.5 \ M \ NaOH$ was added to $500 \ mL$ of $1 \ M \ HCl$. The number of unreacted $HCl$ molecules in the solution after complete reaction is $...... \times 10^{21}$. (Nearest integer) $(N_{A} = 6.022 \times 10^{23})$

Consider the following reaction occurring in the blast furnace: $Fe_3O_{4(s)} + 4CO_{(g)} \rightarrow 3Fe_{(l)} + 4CO_{2(g)}$. '$x$' kg of iron is produced when $2.32 \times 10^3 \ kg$ of $Fe_3O_4$ and $2.8 \times 10^2 \ kg$ of $CO$ are brought together in the furnace. The value of '$x$' is $.............$ (nearest integer). Given: Molar mass of $Fe_3O_4 = 232 \ g \ mol^{-1}$,Molar mass of $CO = 28 \ g \ mol^{-1}$,Molar mass of $Fe = 56 \ g \ mol^{-1}$.

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

When $35 \ mL$ of $0.15 \ M$ lead nitrate solution is mixed with $20 \ mL$ of $0.12 \ M$ chromic sulphate solution,$....... \times 10^{-5}$ moles of lead sulphate precipitate out. (Round off to the Nearest Integer).

What is a limiting reagent?

In the reaction,$4NH_{3(g)} + 5O_{2(g)} \to 4NO_{(g)} + 6H_{2}O_{(g)}$,when $1 \ mole$ of ammonia and $1 \ mole$ of $O_{2}$ are made to react to completion: