Ssurroudnings vs Ssystem

[Alexis Elliott 1J]

I am a bit confused about when to use the equation deltaH/T. Sometimes there is also a negative sign included and I was also wondering when we are supposed to add in that negative sign. What can't we use the equation qrev/T?

Thank you!

[Preston_Dang_1B]

You would add the negative sign relative to which S you are looking at. For example, if you were looking at S_surr and the reaction taking place is endothermic, then that means heat is being lost from the surroundings and going into the system, which means that the surroundings are losing heat, meaning H is negative, assuming reaction is at constant pressure. In the case of S_sys, it is gaining energy from the surroundings which means its respective H is positive and will not require a negative sign when calculating S.

Hope this helps!