Thursday, February 24, 2011

Enthalpy (Energy Calculations)

When converting from kJ-->mol or mol-->kJ, we use delta H to show us the change in energy.
*Remember sig figs apply to these conversions!

Eg. Calculate the energy  absorbed when 50g of BrCl is formed from Br2 and Cl2
      Br2 + Cl2 + 100 kJ----> 2BrCl
50g x1 mole of BrCl x   100kJ=
         ---------------     --------      21 kJ
          115.4g                2BrCl

When kJ is on the right side, it is an positive, endothermic reaction; when the kJ is on the left, it is an negative, exothermic reaction.



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