what is the standard enthalpy of formation of an element?
8166
The standard enthalpy of formation for an element in its standard state is ZERO!!!! Elements in their standard state are not formed, they just are. So, ΔH°f for C (s, graphite) is zero, but the ΔH°f for C (s, diamond) is 2 kJ/mol. That is because graphite is the standard state for carbon, not diamond.
68635
This equation essentially states that the standard enthalpy change of formation is equal to the sum of the standard enthalpies of formation of the products minus the sum of the standard enthalpies of formation of the reactants. and the standard enthalpy of formation values: ΔH fo[A] = 433 KJ/mol.
701710
The standard enthalpy of formation is measured in units of energy per amount of substance, usually stated in kilojoule per mole (kJ mol−1), but also in kilocalorie per mole, joule per mole or kilocalorie per gram (any combination of these units conforming to the energy per mass or amount guideline).
695616
Standard enthalpy of reaction. ... The enthalpy change is defined as the amount of heat absorbed or evolved in the transformation of the reactants at a given temperature and pressure into the products at the same temperature and pressure.
254449
See section on enthalpy for a more detailed explanation. ... The standard enthalpy of reaction is symbolized by ΔHº or ΔHºrxn and can take on both positive and negative values. The units for ΔHº are kiloJoules per mole, or kj/mol.
699447
Thus, the standard heat of formation of glycine is -528.0 kJ/mol, and we have seen how we can determine this quantity without making glycine directly from its elements.
120455
Standard enthalpy changes refer to reactions done under standard conditions, and with everything present in their standard states. Standard states are sometimes referred to as "reference states". Standard conditions. Standard conditions are: 298 K (25°C)
256314
The enthalpy of formation for an element in its elemental state will always be 0 because it takes no energy to form a naturally-occurring compound. ... When a substance is formed from the most stable form of its elements, a change in enthalpy takes place.
244778
standard molar enthalpy of formation: the enthalpy change of a chemical reaction in which one mole of a pure substance is formed from the free elements in their most stable states under standard state conditions.
594699
The standard enthalpy of formation is the change in enthalpy that accompanies the formation of one mole of the compound from its elements. The standard enthalpy of reaction occurs in a system when one mole of matter is transformed by a chemical reaction.
342473
Standard heat of combustion: The energy liberated when a substance X undergoes complete combustion, with excess of oxygen at standard conditions (25°C and 1 bar). In thermodynamical terms it is the negative of the enthalpy change for the combustion reaction.
789594
Yes there is a difference. The reaction enthalpy is the heat given off or taken up for the rxn, i.e., the enthalpy difference between the reactants and products. The enthalpy of formation of a compound is the enthalpy change between the elements in their standard state (reactants) and the compound (product).
1399750
For a chemical reaction, the enthalpy of reaction (ΔHrxn) is the difference in enthalpy between products and reactants; the units of ΔHrxn are kilojoules per mole.
610538
The standard enthalpy of formation of NF3(g) at 25°C is –132.09 kJ/mol.
261210
The enthalpy of formation of ammonia is `-46.0 KJ mol^(-1)` .
172663
['The standard enthalpy of combustion is ΔH∘c .', 'You calculate ΔH∘c from standard enthalpies of formation:', 'For each product, you multiply its ΔH∘f by its coefficient in the balanced equation and add them together.']
698683
The standard enthalpy change of neutralisation is the enthalpy change when solutions of an acid and an alkali react together under standard conditions to produce 1 mole of water. Notice that enthalpy change of neutralisation is always measured per mole of water formed.