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Enthalpy of formation (ΔHf) is the enthalpy change for the formation of 1 mol of a compound from its component elements, such as the formation of carbon dioxide from carbon and oxygen. The formation of any chemical can be as a reaction from the corresponding elements: elements → compound.
26 Αυγ 2023 · Example \(\PageIndex{6}\): Stepwise Calculation of Heat of Formation Using Hess’s Law. Determine the enthalpy of formation, of \(\ce{FeCl3(s)}\) from the enthalpy changes of the following two-step process that occurs under standard state conditions: \[\ce{Fe (s) + Cl2(g) -> FeCl2(s)} \quad \Delta H^{\circ}=-341.8 \, \text{kJ} \nonumber \]
The change in enthalpy for the formation of one mole of CO2 is equal to negative 393.5 kilojoules per one mole of carbon dioxide. Let's look at some more equations showing the formation of one mole of a substance. For example, let's look at the equation showing the formation of one mole of water.
A standard enthalpy of formation Δ H f ° Δ H f ° is an enthalpy change for a reaction in which exactly 1 mole of a pure substance is formed from free elements in their most stable states under standard state conditions. These values are especially useful for computing or predicting enthalpy changes for chemical reactions that are ...
Examples [1-4] 1. Carbon Dioxide (CO 2) C (s, graphite) + O 2 (g) → CO 2 (g) ΔHfo = -393.509 kJ/mol. The standard enthalpy of the formation of carbon dioxide is -393.509 kJ/mol. It means that 393.509 KJ of energy is released when one mole of CO 2 is formed from graphite (C) and oxygen gas (O 2) at 1 atmospheric pressure and 25 ˚C.
ΔH ° rxn = Σ (ΔH f ° products) - Σ (ΔH f ° reactants) signifying the sum of the standard enthalpies of formation of products minus reactants. The units for ΔH f ° are typically kilojoules per mole (kJ/mol), and this equation is pivotal for predicting reaction energetics. Show more.
The standard enthalpy of formation is a measure of the energy released or consumed when one mole of a substance is created under standard conditions from its pure elements. The symbol of the standard enthalpy of formation is ΔH f. Δ = A change in enthalpy. o = A degree signifies that it's a standard enthalpy change.
