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2014-11-16T00:57:15+05:30

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Urea is formed by the following reaction.   Well u can take another reaction and calculate the internal energy too.  Ammonia and carbon dioxide give urea and water.  Formation of Ammonia is exothermic and it releases heat energy.

    2 N H₃ + C O₂  ⇒⇒    H₂ O + CO (NH₂)₂ 

Rule is :  heat of formation of products - heat of formation of reactants is the released energy, ΔH of the reaction.

       ΔH = 285.kJ for water + 333.5kJ for urea
                      - 2 ( 46 kJ) for ammonia - ( 393.5 kJ ) for carbon dioxide
            = 133 kJ 

The change in the internal energy of the products  water and urea will be due to this heat energy released.

Perhaps  increase in internal energy of urea can be calculated by taking the proportion of mass of urea in the products.

2 5 2
thanx for selecting best answer. u r welcome
welcome sir!!