Learning Competencies
- Explain the enthalpy of a reaction. (STEM-GC11TC-IIIg-i-125)
- Write the thermochemical equation for a chemical reaction. (STEM-GC11TC-IIIg-i-126)
- Calculate the change in enthalpy of a given reaction using Hess Law. (STEM-GC11TC-IIIg-i-127)
At the end of the lesson, the learners will be able to:
• define enthalpy of reaction;
• write thermochemical equations;
• interpret thermochemical equations;
• state Hess’ Law in own words; and
• determine the enthalpy of reactions from known thermochemical data using Hess’ Law.
Thermochemistry is a critical field of study because it helps to determine if a particular reaction will occur and if it will release or absorb energy.
A thermochemical equation is a balanced chemical equation in which the exact value of enthalpy change, physical states, and the number of moles of reactants and products are specified.
Hess’s law states that When reactants are converted to products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps.
Calculate the heat released in kJ per gram of Al reacting with Fe2O3. The enthalpy of formation for Fe (l) is 12.40 kJ/mol.