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Standard enthalpy of combustion is the enthalpy change when one mole of an organic compound reacts with molecular oxygen (O 2) to form carbon dioxide and liquid water. For example, the standard enthalpy of combustion of ethane gas refers to the reaction C 2 H 6 (g) + (7/2) O 2 (g) → 2 CO 2 (g) + 3 H 2 O (l). Standard enthalpy of formation is ...
For a fuel of composition C c H h O o N n, the (higher) heat of combustion is 419 kJ/mol × (c + 0.3 h − 0.5 o) usually to a good approximation (±3%), [2] [3] though it gives poor results for some compounds such as (gaseous) formaldehyde and carbon monoxide, and can be significantly off if o + n > c, such as for glycerine dinitrate, C 3 H 6 ...
For many substances, the formation reaction may be considered as the sum of a number of simpler reactions, either real or fictitious. The enthalpy of reaction can then be analyzed by applying Hess' law, which states that the sum of the enthalpy changes for a number of individual reaction steps equals the enthalpy change of the overall reaction.
Enthalpy is the transfer of energy in a reaction (for chemical reactions, it is in the form of heat) and is the change in enthalpy. Δ H {\displaystyle \Delta H} is a state function, meaning that Δ H {\displaystyle \Delta H} is independent of processes occurring between initial and final states.
Quantity (common name/s) (Common) symbol/s Defining equation SI unit Dimension Temperature gradient: No standard symbol K⋅m −1: ΘL −1: Thermal conduction rate, thermal current, thermal/heat flux, thermal power transfer
C p is infinite at phase transition temperatures because the enthalpy changes isothermally. At the Curie temperature, C p shows a sharp discontinuity while the enthalpy has a change in slope. Values of ΔH are usually given for the transition at the normal standard state temperature for the two states, and if so, are designated with a ...
Enthalpy of combustion, Δ c H o liquid –1236.4 kJ/mol Heat capacity, c p: 129.0 J/(mol K) Gas properties Std enthalpy change of formation, ...
The Mollier enthalpy–entropy diagram for water and steam. The "dryness fraction", x , gives the fraction by mass of gaseous water in the wet region, the remainder being droplets of liquid. An enthalpy–entropy chart , also known as the H – S chart or Mollier diagram , plots the total heat against entropy, [ 1 ] describing the enthalpy of a ...