Why is ΔH for an exothermic reaction negative (focusing on the Born Haber Cycle)?
Ok, first you need to understand that heat isn’t actually “negative.” The negative isn’t all that important. It’s just a way of showing that heat is released. It has no other meaning or importance other than that. You could make ΔH positive if you wanted. The problem with that is that there needs to be some way of indicating which way the heat is flowing so a bunch of scientists decided that we should make the sign negative to indicate that heat is flowing out of the system and into the surroundings. If you want a more clear idea of why they decided to make heat leaving the system negative then think about this; when heat leaves the system you could say the system is loosing heat. Now when you lose something you represent that with a negative value to indicate that you’ve lost something instead of gaining. It’s like if you have zero dollars and you borrow 4 dollars from someone, well now you have zero dollars and you owe someone 4 dollars so we say you have negative 4 dollars, $-4 whic