CHEMISTRY COMMUNITY

Hello! Can someone please explain how to reason through question 3B on the midterm. I understand that the combination of HCl and NaOH would be a strong base and a strong acid being titrated, but I am confused on how to pick which combination would give the largest deltaT. I guess I am just a bit confused on how the titration relates to temperature change?

Thanks!

So for this question, you have to look at what system will have the smallest volume and the greatest amount of substance that is concentrated in it. My TA explained it in the way that a smaller volume will allow for a greater concentration of substrate to interact, and a higher concentration will also do the same, so the species' will interact and have a larger change in temperature.

I just knew from AP Chem that neutralization reactions are exothermic. So for this question, I just determined which reaction had the most moles of reaction in the smallest amount of liquid. The more liquid there is, the more heat that can be absorbed without increasing the temperature much. In other words, if there is only a little bit of liquid, the reaction can have a greater increase in temperature with the same amount of heat released.

You can think about it in terms of which reaction will be the strongest. The strongest chemical reaction would give off the most amount of heat energy when producing the products. If you allow two diluted substances to react, you wouldn't see a strong enough result as compared to if you reacted a highly concentrated strong acid with a highly concentrated strong base. The most concentrated versions of the reactants would be answer choice (B) because they have the highest molarity and the smallest volumes.