8.12.2011

Compare exothermic and endothermic reaction?


  • EXOTHERMIC REACTION:
  • DEFINITION: ENERGY RELEASING REACTIONA ARE SAID TO BE EXOTHERMIC.
  • EXPLANATION: We know that bond breaking always consumes energy and that bond making always releases energy. The balance between these two processes results in two types of reactions. When the energy released by bond forming is greater than energy consumed by bond breaking there is a net release of chemical energy by the reaction. In an exothermic reaction energy is transferred to the surroundings.
  • EXAMPLES:
  • The reactions of fuels with oxygen of the air are all highly exothermic and the energy released can be used as a heating source, cooking meal or to drive an engine.
  • 2.       C(s)+O2(g)àCO2(g)   +∆H= -393.5 kj/mol
  • 3.       H2(g)+O2 (g)à H2O  ∆H= -242 kj/mol                 
  • CONCLUSION: In simple words, chemical reactions in which heat is evolved are called exothermic reactions.
  • ENDOTHERMIC REACTIONS:
  • DEFINITION: ENERGY ABSORBING REACTIONS ARE SAID TO BE ENDOTHERMIC.
  • EXPLANATION: When the energy of bond breaking is greater than the energy of bond forming, the chemical reaction must be driven by the energy absorbed from the surroundings.
  • EXAMPLES:
  • 1.       Conversion of liquid water into its vapors is an endothermic process.
  • 2.       H2O(l)àH2O2 (g) ∆H= +40.7 kj/mol

  •       3.       H2+I2à2 HI(g)  ∆H=52.96 kj/mol
  •       4.       N2 +O2à 2NO ∆H=180.6 kj/mol
  • CONCLUSION: In other words, chemical reactions which are accompanied by the absorption of heat are called endothermic reactions.

2 comments:

  1. you are doing very good job.its really very helpful. please give me some details about Wander Vaals equation for entry test.

    ReplyDelete
  2. you are doing very good job.its really very helpful. please give me some details about Wander Vaals equation for entry test.

    ReplyDelete

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