Using Heats of Formation
From the First Law of Thermodynamics, it can be seen that the enthalpy of a reaction can be determined from the heats of formation reagents and products:
ΔHrxn=ΣΔHf(prods)-ΣΔHf(reags)
This pages presents "generic" problems to provide practice in applying the above relationship. The problems are generic in that basic symbols are used to represent the chemical species rather that using actual chemical formulae. Further, to emphasize the methodology rather than the numbers, all heats of formation will have one sig figure and be between 10 and 100.
- When you press new problem, a "balanced chemical equation" and a table of heats of formation will be presented to the right of the table.
- Calculate the heat of the reaction, enter it in the answer cell and press "Check Answer."
- If you miss a problem three or more times, pressing the "Show Answer" button will display a complete solution.