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Review
You may wish to review the Laws of Thermochemistry and Endothermic and Exothermic Reactions before you begin.
Problem
For the decomposition of hydrogen peroxide, it is known that:
H2O2(l) --> H2O(l) + 1/2 O2(g); DH = -98.2 kJ
Using this information, determine DH for the reaction:
2 H2O(l) + O2(g) --> 2 H2O2(l)
Solution
From the laws of thermochemistry, you know that the change in enthalpy is directly proportional to the quantity of a substance in a reaction and that the change in enthalphy for a reaction is equal in magnitude but opposite in sign to DH for the reverse reaction. Applying these rules:
2 H2O2(l) --> 2 H2O(l) + O2(g); DH = -196.4 kJ
2 H2O(l) + O2(g) --> 2 H2O2(l); DH = +196.4 kJ
Answer
+196.4 kJ
First page > Sample Problem #1 > Page 1, 2, 3
