Answer to Question #316484 in General Chemistry for John

Question

1. Define heat of formation/standard heat of formation ΔHfo.

2. Discuss standard state and give examples (Padolina et al., 1995).

3. State that values of standard states of formation are important because these are conveniently used to calculate changes in enthalpy, ΔH of many reactions.

4. Give examples that illustrate the use of standard heats of formation in calculating changes in enthalpy or ΔH of reactions.

please answer correctly

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DEADLINE : 03/26/2022

Answer 1

1. The heat of formation/standard heat of formation is the amount of heat absorbed or released when one mole of a compound is formed from its constituent elements, each substance being in its normal state of aggregation (gas, liquid, or solid).
2. We define the standard state of a substance at any particular temperature as the most stable form of this substance at a pressure of one bar. For example, for water at -10 °C, the standard state is ice at a pressure of one bar; at +10 °C it is liquid water at a pressure of one bar.
3. If we have values for the corresponding standard enthalpies of education, we can determine the change in enthalpies for any reaction according to Hess's law.
4. The standard heat of formation of an element in its most stable form is zero. The standard enthalpy of reaction can be calculated from the sum of the standard enthalpies of formation of the products (each multiplied by its stoichiometric coefficient) minus the sum of the standard enthalpies of formation of the reactants (each multiplied by its stoichiometric coefficient) - the products minus reactants rule.