Zain786H
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I got the answer to this q wrong as -1046, not sure where I went wrong, did I do my arrows right for the formation hess cycle?
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rzi999
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Enthalpy of formation is defined as the enthalpy change when one mole of a substance is formed from it's elements. This means that when drawing the Hess cycle the arrows should both be pointed up to show NH4NO3 being formed from its constituent elements. Should be easy to work out after that
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Zain786H
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(Original post by EverythingGreen)
Enthalpy of formation is defined as the enthalpy change when one mole of a substance is formed from it's elements. This means that when drawing the Hess cycle the arrows should both be pointed up to show NH4NO3 being formed from its constituent elements. Should be easy to work out after that
is this in all cases that the arrows go up? thanks
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AftabGujral
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The table gives you the enthalpy of formation of the products and the reactants. All you need to work out is the sum of the enthalpy of formation of reactants and the sum of the enthalpy of formation of products. Then

Delta H (reaction) = (sum of the enthalpy of formation of products) - (sum of the enthalpy of formation of reactants)
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C_Yap
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the arrow pointing to nh4no3 is wrong way round.

enthalpy of formation is from the constituent elements
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AftabGujral
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(Original post by C_Yap)
the arrow pointing to nh4no3 is wrong way round.

enthalpy of formation is from the constituent elements
Yes, that was the error in the diagram.

(Although you can do the question without drawing a Hess's Law Cycle)
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