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The Van 't Hoff equation relates the change in the equilibrium constant, K eq, of a chemical reaction to the change in temperature, T, given the standard enthalpy change, Δ r H โ, for the process. The subscript r {\displaystyle r} means "reaction" and the superscript โ {\displaystyle \ominus } means "standard".
Thus, an endothermic reaction generally leads to an increase in the temperature of the system and a decrease in that of the surroundings. [1] The term was coined by 19th-century French chemist Marcellin Berthelot. [3] The term endothermic comes from the Greek แผνδον (endon) meaning 'within' and θερμ- (therm) meaning 'hot' or 'warm'. [4]
In thermodynamics, the enthalpy of mixing (also heat of mixing and excess enthalpy) is the enthalpy liberated or absorbed from a substance upon mixing. [1] When a substance or compound is combined with any other substance or compound, the enthalpy of mixing is the consequence of the new interactions between the two substances or compounds. [1]
In thermochemistry, a thermochemical equation is a balanced chemical equation that represents the energy changes from a system to its surroundings. One such equation involves the enthalpy change, which is denoted with Δ H {\displaystyle \Delta H} In variable form, a thermochemical equation would appear similar to the following:
Thermochemistry is the study of the heat energy which is associated with chemical reactions and/or phase changes such as melting and boiling. A reaction may release or absorb energy, and a phase change may do the same. Thermochemistry focuses on the energy exchange between a system and its surroundings in the form of heat. Thermochemistry is ...
In physics, chemistry, and other related fields like biology, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states of matter : solid , liquid , and gas , and in rare cases, plasma .
If the enthalpy changes are known for all the equations in the sequence, their sum will be the enthalpy change for the net equation. If the net enthalpy change is negative ( Δ H net < 0 {\displaystyle \Delta H_{\text{net}}<0} ), the reaction is exothermic and is more likely to be spontaneous ; positive Δ H values correspond to endothermic ...
Enthalpy change of solution for some selected compounds: hydrochloric acid-74.84 ammonium nitrate +25.69 ammonia-30.50 potassium hydroxide-57.61 caesium hydroxide-71.55 sodium chloride +3.87 potassium chlorate +41.38 acetic acid-1.51 sodium hydroxide-44.50 Change in enthalpy ΔH o in kJ/mol in water at 25°C [2]