enow.com Web Search

Search results

  1. Results from the WOW.Com Content Network
  2. Standard enthalpy of formation - Wikipedia

    en.wikipedia.org/wiki/Standard_enthalpy_of_formation

    Since the pressure of the standard formation reaction is fixed at 1 bar, the standard formation enthalpy or reaction heat is a function of temperature. For tabulation purposes, standard formation enthalpies are all given at a single temperature: 298 K, represented by the symbol Δ f H ⦵ 298 K.

  3. Standard enthalpy of reaction - Wikipedia

    en.wikipedia.org/wiki/Standard_enthalpy_of_reaction

    The enthalpy of formation of one mole of ethane gas refers to the reaction 2 C (graphite) + 3 H 2 (g) → C 2 H 6 (g). Standard enthalpy of hydrogenation is defined as the enthalpy change observed when one mole of an unsaturated compound reacts with an excess of hydrogen to become fully saturated.

  4. Thermodynamic databases for pure substances - Wikipedia

    en.wikipedia.org/wiki/Thermodynamic_databases...

    The enthalpy change for any standard reaction is designated ΔH° rx. Standard molar heat of formation of ZnBr 2 (c,l) from the elements, showing discontinuities at transition temperatures of the elements and the compound.

  5. Enthalpy - Wikipedia

    en.wikipedia.org/wiki/Enthalpy

    Enthalpies and enthalpy changes for reactions vary as a function of temperature, [5] but tables generally list the standard heats of formation of substances at 25 °C (298 K). For endothermic (heat-absorbing) processes, the change Δ H is a positive value; for exothermic (heat-releasing) processes it is negative.

  6. Heat of combustion - Wikipedia

    en.wikipedia.org/wiki/Heat_of_combustion

    There are two kinds of enthalpy of combustion, called high(er) and low(er) heat(ing) value, depending on how much the products are allowed to cool and whether compounds like H 2 O are allowed to condense. The high heat values are conventionally measured with a bomb calorimeter. Low heat values are calculated from high heat value test data.

  7. Enthalpy of fusion - Wikipedia

    en.wikipedia.org/wiki/Enthalpy_of_fusion

    Enthalpies of melting and boiling for pure elements versus temperatures of transition, demonstrating Trouton's rule. In thermodynamics, the enthalpy of fusion of a substance, also known as (latent) heat of fusion, is the change in its enthalpy resulting from providing energy, typically heat, to a specific quantity of the substance to change its state from a solid to a liquid, at constant pressure.

  8. Thermochemistry - Wikipedia

    en.wikipedia.org/wiki/Thermochemistry

    Endothermic reactions absorb heat, while exothermic reactions release heat. Thermochemistry coalesces the concepts of thermodynamics with the concept of energy in the form of chemical bonds. The subject commonly includes calculations of such quantities as heat capacity, heat of combustion, heat of formation, enthalpy, entropy, and free energy.

  9. Van 't Hoff equation - Wikipedia

    en.wikipedia.org/wiki/Van_'t_Hoff_equation

    However, in some cases the enthalpy and entropy do change dramatically with temperature. A first-order approximation is to assume that the two different reaction products have different heat capacities. Incorporating this assumption yields an additional term ⁠ c / T 2 ⁠ in the expression for the equilibrium constant as a function of ...