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

$A$ reaction gas mixture contains $50 \%$,$30 \%$,and $20 \%$ of $A$,$B$,and $C$ by volume,respectively. The mixture undergoes the following reactions:
$1. A + 2B \rightarrow P_1$
$2. 4P_1 + 3C \rightarrow P_2$
$P_1$ and $P_2$ are two products of the reactions. Choose the correct answer if the reaction completes.

When $30 \ mL$ of $H_2$ reacts with $20 \ mL$ of $O_2$ to form water,what is leftover when the reaction ends?

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:

The maximum amount of $BaSO_4$ precipitated on mixing $BaCl_2$ $(0.5 \ M)$ with $H_2SO_4$ $(1 \ M)$ will correspond to.....$M$

Butane reacts with oxygen to produce carbon dioxide and water following the equation given below: $C_4H_{10(g)} + \frac{13}{2} O_{2(g)} \rightarrow 4 CO_{2(g)} + 5 H_2O_{(l)}$. If $174.0 \ kg$ of butane is mixed with $320.0 \ kg$ of $O_2$,the volume of water formed in litres is $...........$ (Nearest integer). [$Given$: $(a)$ Molar mass of $C, H, O$ are $12, 1, 16 \ g \ mol^{-1}$ respectively,$(b)$ Density of water $= 1 \ g \ mL^{-1}$]