Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (d) Rubbing alcohol evaporates from your skin.

Video transcript

hi everyone for this problem. It reads which process below has the correct sign for entropy of reaction and correct classification. Endo thermic or eggs A thermic. So we're looking for the correct sign for delta H. And the correct classification of endo thermic and eggs A thermic. Okay, so let's go ahead and write down our definitions for both. So we have endo thermic and X. A. Thermic. Okay. And these terms classify or represent entropy of a reaction. So in simple terms the entropy of a reaction is determined by the net energy change that occurs during a reaction. And so we want to think about this in terms of heat. Okay, so let's write down here heat for a endo thermic reaction. Heat is being absorbed by the system. Okay. And with heat being absorbed by the system. What this means in terms of the sign for our entropy of reaction is the sign is going to be positive for an exotic thermic reaction. He is being released by the system. So what this means in terms of the sign for the entropy of the reaction is the sign is going to be negative. So now that we know what sign associates with both Endo thermic and eggs A thermic. So let's take a look at our answer choices for answer choice. A photosynthesis it says here that the entropy of the reaction is going to be negative and endo thermic So photosynthesis requires energy. So if it requires energy that means heat is being absorbed. And so that means that photosynthesis is endo thermic Okay, if photosynthesis is endo thermic that means it's going to have a positive delta H. Okay so here we can see that this answer choice is incorrect. Alright because they do not match the be burning a piece of paper. Okay so burning a piece of paper is combustion. Okay and a combustion is eggs. Ah thermic. Okay because heat is being released by the system. So combustion is eggs A thermic. So that means the sign for delta H. Is going to be a negative delta H. Alright. And so we can see here that B. Is incorrect for answer choice. C. Baking soda neutralizes vinegar. So a neutralization reaction is eggs A thermic with it being exons thermic that means heat is being released by the system. Okay, so that means then the sign for our change in entropy is going to be negative. So this is incorrect. Lastly answer choice. D. A firework display a firework display is a combustion. He is being released. Okay, so that means that this is a eggs ah thermic process. So if this is an exotic thermic process and he is being released. The sign for our change in entropy is going to be a negative delta H. And here we see that X. Ah thermic and our sign both match. So that is going to make answer choice. D. The correct answer. Okay this is the process that has the correct sign for change in entropy and the correct classification. That's it for this problem. I hope this was helpful.