Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Energy of products in endothermic reaction

  1. Aug 4, 2012 #1
    How is the energy of products in endothermic reaction more than the energy of reactants
    When we see the following equation of an endothermic reaction below
    2H2O2--> 2H2O + O2
    The 2H2O2 has an enthalpy of 2144 whereas the products have and enthalpy of 1424 Kj/mol

    SO the reactants have more enthalpy than the products but the reaction is still endothermic. Why is that?

    Can someone please explain this to me. Please I know this is a simple and silly question but I won't understand my energy chapter until and unless I don't know the answer of this query.
  2. jcsd
  3. Aug 4, 2012 #2
    Can somebody please help. I'm really desperate.
  4. Aug 4, 2012 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Why do you think the decomposition of hydrogen peroxide is endothermic?
  5. Aug 4, 2012 #4
    I was always told that decomposition is endothermic? It's in my book.

    Also in a related question concerning Methane combustion the reactants have a Delta H of 2548 whereas the products have a delta H of 3324.

    Again combustion is definitely exothermic but how come the Reactants have less energy than the products?
  6. Aug 4, 2012 #5
    There is something that I really need to understand which is what does it exactly mean when it is said that Products have less energy/ more energy than reactants?
    Do they individually measure the energies of each chemical and how do they do that?

    Or are the talking about the energy that is taken to make and break bonds etc.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook