Stoichiometry — Percentage Composition — Empirical & Molecular Formula — Chemical Equations — Question 4

[By Lussac's law]

$\begin{matrix} \text{H}_2 & + & \text{Cl}_2 &\longrightarrow & 2\text{HCl} \\ 1 \text{ vol.} & : & 1 \text{ vol.} & \longrightarrow & 2\text{ vol.} \end{matrix}$

To calculate the amount of hydrogen used:

$\begin{matrix}\text{Cl}_2 & : & \text{H}_2 \\ 1 \text{ vol.} & : & 1 \text{ vol.} \\ 4 \text{ lit.} & : & \text{x} \end{matrix}$

∴

$x = \dfrac{1}{1} \times 4 = 4 \text{ lit.}$

Remaining hydrogen = 6 - 4 = 2 lit.

To calculate the amount of HCl :

$\begin{matrix}\text{Cl}_2 & : & \text{HCl} \\ 1 \text{ vol.} & : & 2 \text{ vol.} \\ 4 \text{ lit.} & : & \text{x} \end{matrix}$

∴

$x = \dfrac{2}{1} \times 4 = 8 \text{ lit.}$

Hence, after reaction 8 lit of HCl is formed which dissolves in water and 2 lit of hydrogen is left.

∴ 2 lits. of hydrogen is left.