A volume of a gaseous hydrocarbon is exploded with a large excess of oxygen gas in a sealed eudiomet — States of Matter and Gaseous State Chemistry Question
Question
A volume $V$ of a gaseous hydrocarbon $C_xH_y$ is exploded with a large excess of oxygen gas in a sealed eudiometer tube. After the explosion, the system is cooled back to the initial room temperature. Assuming water condenses to a liquid of negligible volume, which of the following mathematical expressions correctly describe the stoichiometry of this process?
💡 Solution & Explanation
The general combustion equation is $C_xH_y(g) + (x + y/4)O_2(g) \rightarrow xCO_2(g) + (y/2)H_2O(l)$. From this, $1\text{ volume}$ of $HC$ consumes $(x + y/4)\text{ volumes}$ of $O_2$ and produces $x\text{ volumes}$ of $CO_2$. So $V_{CO_2} = xV$ and $O_2\text{ consumed} = V(x+y/4)$. Contraction = $V_{reactants} - V_{products(g)} = [V + V(x+y/4)] - [xV] = V + Vx + Vy/4 - Vx = V(1 + y/4)$. $KOH$ absorbs the $CO_2$, so the further contraction is $xV$.