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Hess's law Watch

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    Hi anyone know an easy and none confusing way of constructing a Hess cycle for standard enthalpy of formation and standard enthalpy of combustion reactions? I am studying it at school but am really confused on the whole use of the arrows and how to get a final answer for the enthalpy of the reaction.
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    (Original post by Logic4Life)
    Hi anyone know an easy and none confusing way of constructing a Hess cycle for standard enthalpy of formation and standard enthalpy of combustion reactions? I am studying it at school but am really confused on the whole use of the arrows and how to get a final answer for the enthalpy of the reaction.
    I go with clockwise = anti-clockwise when I teach it. Usually goes down well with the learners.
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    Aww cycles are confusing! Just remember these equations:

    Standard Enthalpy of Formation= Sum of products-Sum of reactants.


    Standard Enthalpy of Combustion= Sum of reactants-Sum of products.
    CRP (almost like crap; combustion, reactants, products)


    Mean Bond Enthalpy= Sum of bonds broken- Sum of bonds made.
    BBBM (almost like BBM as in Blackberry Messenger)

    I know it's silly but some people find this helpful.


    Oh and please assume that all reactants and products in my equations are in their standard states and under standard conditions.




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    (Original post by Mimi97)
    Aww cycles are confusing! Just remember these equations:

    Standard Enthalpy of Formation= Sum of products-Sum of reactants.


    Standard Enthalpy of Combustion= Sum of reactants-Sum of products.
    CRP (almost like crap; combustion, reactants, products)


    Mean Bond Enthalpy= Sum of bonds broken- Sum of bonds made.
    BBBM (almost like BBM as in Blackberry Messenger)

    I know it's silly but some people find this helpful.


    Oh and please assume that all reactants and products in my equations are in their standard states and under standard conditions.




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    Is it not necessary to know the triangle/diagram way of figuring it out- even for A2? Can I just memorise those things? ^
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    (Original post by ChronicBoredom)
    Is it not necessary to know the triangle/diagram way of figuring it out- even for A2? Can I just memorise those things? ^
    Don't recommend trying to memorise equations without some logic behind it. Check out this interactive on Hess's law
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    (Original post by charco)
    Don't recommend trying to memorise equations without some logic behind it. Check out this interactive on Hess's law
    It's not that, I just don't like having to draw out the whole cycle. Will I lose marks if I don't draw the whole cycle?
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    (Original post by ChronicBoredom)
    It's not that, I just don't like having to draw out the whole cycle. Will I lose marks if I don't draw the whole cycle?
    If the question asks you to draw the cycle, then yes.
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    (Original post by charco)
    If the question asks you to draw the cycle, then yes.
    lol ok, thanks
 
 
 
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