In exothermic reactions why does the temperature reach a maximum point and then start falling?
Using the example of a copper salt and sodium hydroxide solution, why does the temp reach a maximum point then start to fall even when you add more NaOH is it because all of the copper salt has reacted?
- Thread Starter
- 28-05-2016 23:38
- 29-05-2016 00:18
I'm pretty terrible at chemistry but I'll try my best to answer that question.
So yes, exothermic reaction means that the reaction produces thermal energy, heating up the solution, so temperature increases.
As the reaction progresses, more thermal energy produced, more heat transferred to the solution, so the temperature continues to rise.
However... the same time as this is occurring, the rate of reaction is also decreasing, as the concentration of reactants are decreasing (as you said)
The catch is this. As the temperature continues to rise (above room temperature/surroundings), the temperature gradient between the solution and surroundings increase, so more and more heat at a greater rate is being transferred to the surroundings. Essentially, there's two opposing trends: The heat being produced from the reaction, and the heat being taken away by the surroundings.
So eventually when the heat being taken away from the reaction exceeds the heat being produced by the reaction, the temperature will start to decrease. And of course, this will eventually happen because as you said the rate of reaction is decreasing all the time.
Hope I helped a tiny bit!