What is the difference between the internal energy change ∆E and the enthalpy change ∆H? Which of the two is mea- sured at constant pressure and which at constant volume?

Video transcript

Hello everyone today. We have been given the falling problem. The internal energy and the entropy change are the same for reaction and both are measured at constant pressure. Is this statement true or false? So we want to determine or define what these variables mean. So internal energy or delta E. Is referred to as the change in heat that happens to a reaction at constant volume. So when a reaction takes place and the volume is constant but we have a change in heat. We are having a change in the internal energy. And so this indicates there is no change in our volume. So that stays zero. Delta V stands for a change in volume it stays zero. And thus we have no work being done. Why? Because the equation for work is pressure times volume and a volume is zero. Then of course our work will be zero P. On the other hand or delta H is the change in heat. Once again it's gonna be our change in the heat energy to a reaction at constant pressure. So we see here both entropy and internal energy are very similar. However, one deals with constant volume and one deals with constant pressure and so in this situation since volume is not equal to zero we can then have work. So this statement is actually false. Once again it is false because NLP and internal energy are two separate variables and work can be done even if volume even if the pressure is kept constant with NLP And with that we've answered our question overall, I hope that this helped and until next time.