| Chemical equilibrium reactions | are chemical reactions in which the reactants are depleted at exactly the same rate as they are replenished from the products by the reverse reaction. At equilibrium the reaction proceeds in both directions at the same rate.
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| Criterion for chemical equilibrium | is the equation set equal to zero that involves the stoichiometric coefficients and the molar Gibbs functions of the reactants and the products in the equilibrium reaction.
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| Equilibrium constant | for an equilibrium reaction is the ratio of the product of the product component's partial pressure raised to their stoichiometric coefficients and the product of the reactant component's partial pressure raised to their stoichiometric coefficients. The equilibrium constant of an ideal-gas mixture at a specified temperature can be determined from knowledge of the standard-state Gibbs function change at the same temperature. The number of equilibrium constant relations needed to determine the equilibrium composition of a reacting mixture is equal to the number of chemical species minus the number of elements present in equilibrium.
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| Gibbs function | is defined as the enthalpy minus the product of the temperature and entropy (G = H – TS).
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| Gibbs phase rule | provides the number of independent variables associated with a multicomponent, multiphase system.
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| Henry's constant | is the product of the total pressure of the gas mixture and the mole fraction of a specie in the liquid phase.
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| Henry's law | states that the mole fraction of a weakly soluble gas in the liquid is equal to the partial pressure of the gas outside the liquid divided by Henry's constant.
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| Inert gas | is a gaseous component in a chemical reaction that does not react chemically with the other components. The presence of inert gases affects the equilibrium composition (although it does not affect the equilibrium constant).
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| Phase equilibrium | is the condition that the two phases of a pure substance are in equilibrium when each phase has the same value of specific Gibbs function. Also, at the triple point (the state at which all three phases coexist in equilibrium), the specific Gibbs function of each one of the three phases is equal.
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| Partial pressure | is the pressure of a component in a gas mixture defined by Dalton's law as the product of the mole fraction and the mixture pressure.
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| Raoult's law | applies to a gas-liquid mixture when a gas is highly soluble in a liquid (such as ammonia in water) and relates the mole fractions of the species of a two-phase mixture in the liquid and gas phases in an approximate manner.
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| Simultaneous reactions | are chemical reactions that involve two or more reactions occurring at the same time.
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| Solubility | represents the maximum amount of solid that can be dissolved in a liquid at a specified temperature.
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| Standard-state Gibbs function change | is the difference between the sum products of the stoichiometric coefficients and the Gibbs function of a component at 1 atm pressure and temperature T for the products and reactants in the stoichiometric reaction.
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| Stoichiometric coefficients | are the mole numbers in the stoichiometric (theoretical) reaction.
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| Stoichiometric (theoretical) reaction | is the balanced reaction equation for a chemical equilibrium reaction.
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| van't Hoff equation | is the expression of the variation of the chemical equilibrium constant with temperature in terms of the enthalpy of reaction at temperature T.
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