A specific photochemical reaction proceeds by absorbing light and is experimentally confirmed to fol — Chemical Kinetics Chemistry Question
Question
A specific photochemical reaction $A \xrightarrow{h u} \text{Products}$ proceeds by absorbing light and is experimentally confirmed to follow strict zero-order kinetics. The initial concentration of $A$ is $0.50 \text{ M}$. If the reaction is exactly $20\%$ complete in $10.0 \text{ minutes}$ under a constant uniform light source, what is the total integrated time required (in minutes) for the reaction to reach absolute $100\%$ completion?
💡 Solution & Explanation
For a zero-order photochemical reaction, the reaction rate is absolutely constant and fully independent of the remaining reactant concentration. The consumption of the reactant is purely linear over time. Since a $20\%$ fraction of the reactant is consumed in exactly $10 \text{ minutes}$, consuming the full $100\%$ will require $5$ times as long. Time for $100\%$ completion $= (100 / 20) \times 10 \text{ minutes} = 5 \times 10 = 50 \text{ minutes}$.