Enthalpy change is also known as heat of reaction, enthalpy of reaction, change in heat content.

Can We Help with Your Assignment?

Let us do your homework! Professional writers in all subject areas are available and will meet your assignment deadline. Free proofreading and copy-editing included.

Enthalpy = total energy of a system

It is impossible to measure the total kinetic and potential energy of a system, so instead we measure enthalpy change (using calorimeters).

Enthalpy Change –  is the energy absorbed from or released to the surroundings when a system changes from reactants to products.  It is given the symbol, DH.

DH = DHproducts DHreactants

DH is measured at STP or SATP for allowance of comparisons between enthalpy changes.

This idea is consistent with the law of conservation of energy, therefore;

Enthalpy change of system  =  quantity of heat that flows from system to  surroundings or vice versa

In other words;

DH  = ± q (DH= Delta H- Enthalpy Change)

Sign of DH

Endothermic Reaction:

  • System has absorbed heat energy from surroundings
  • Hproducts >  Hreactants
  • DH = Hproducts –  Hreactants

= positive value

  • DH is positive

Exothermic Reaction:

  • System releases heat energy into surroundings
  • Hproducts < Hreactants
  • DH = Hproducts –  Hreactants

= negative value

  • DH is negative

Cite this article as: William Anderson (Schoolworkhelper Editorial Team), "Enthalpy Change," in SchoolWorkHelper, 2019, https://schoolworkhelper.net/enthalpy-change/.
guest
0 Comments
Inline Feedbacks
View all comments