Homework Help

why does AN ENTHALPY CHANGE SHOW A POSITIVE sign in endothermic reaction and a...

user profile pic

tubee | Student, Grade 10 | Salutatorian

Posted April 20, 2013 at 9:12 AM via web

dislike 2 like

why does AN ENTHALPY CHANGE SHOW A POSITIVE sign in endothermic reaction and a negative signin exothermic reaction?

Tagged with chemistry, science

1 Answer | Add Yours

user profile pic

jerichorayel | College Teacher | (Level 1) Senior Educator

Posted April 22, 2013 at 5:45 AM (Answer #1)

dislike 2 like

In thermodynamics, exothermic and endothermic are used to define the direction or flow of energy in a system. Exothermic or outside heating is the process of releasing energy out of the system. In other words, exothermic reaction produces heat and sometimes can be explosive. Endothermic on the other hand is a process where in a system absorbs energy from the surrounding in the form of heat. 

They are forms of energy but they have different direction in relevance to a system so there is a need to differentiate them. 

For formal notations, endothermic reaction will have a positive sign or `Delta H > 0` , and exothermic will have a negative sign or `Delta H < 0` . 

Sources:

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes