Question

Illustrate Gay-Lussac's Law of combining volumes by referring to the reaction between :

(b) ethane$\left({\mathrm{C}}_2{\mathrm{H}}_6\right)$ and oxygen to form carbon dioxide

Answer 1

Gay-Lussac's Law of combining volumes:

• According to this law, when gases react to form new gases, the ratio of the volume of gaseous reactants to the gaseous products is expressed as simple whole number ratio. The conditions required are constant pressure and temperature.
• This law is only applicable to gases. As a result, the volumes of solids and liquids are assumed to be zero.

Reaction between ethane$\left({\mathrm{C}}_2{\mathrm{H}}_6\right)$ and oxygen$\left({\mathrm{O}}_2\right)$:

• $2$ volumes of ethane react with $7$volumes of oxygen to form $4$ volumes of carbon dioxide $\left({\mathrm{CO}}_2\right)$ and $6$ volumes of water$\left({\mathrm{H}}_2\mathrm{O}\right)$ at the same pressure and temperature.
• The reaction is as follows:

$$\begin{gathered} 2{\mathrm{C}}_2{\mathrm{H}}_6\left(\mathrm{g}\right)+7{\mathrm{O}}_2\left(\mathrm{g}\right)\to 4{\mathrm{CO}}_2\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right) \\ 2\mathrm{vols}7\mathrm{vols}4\mathrm{vols}6\mathrm{vols} \end{gathered}$$

• The ratio between the volumes of gaseous reactants and products is $2:7:4:6$. This is a simple whole-number ratio.