Raoult's law: Difference between revisions

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(New page: '''Raoult's law''' states that the vapour pressure of an ideal solution of two components :<math>P_v = X_A P^*_{v,A} + X_B P^*_{v,B}</math> category: classical thermodynamics)
 
(Extension to other solutions.)
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'''Raoult's law''' states that the  [[vapour pressure]] of an [[ideal solution]] of two components
'''Raoult's law''' states that the  [[vapour pressure]] of an [[ideal solution]] of two components is:
:<math>P_v = X_A P^*_{v,A} + X_B P^*_{v,B}</math>
:<math>P_v = X_A P^*_{v,A} + X_B P^*_{v,B}</math>
where <math>X_i</math> is the [[molar fraction]] of component i, and <math>P^*_{v,i}</math> is the vapour pressure of pure i.
More generally, '''Raoult's law''' describes the [[partial pressure]] of  component A in the vapour coexisting with a liquid mixture as:
:<math>  P_A = X_A P^*_{v,A} </math>.
This law is obeyed for all components of an ideal solution, and is also obeyed for the solvent of an [[ideal dilute solution]]. The solute's partial pressure of such solutions then obey [[ Henry's law]]. Ideal dilute solutions describe the limiting behavior of a mixture of infinite dilution. Therefore, all solutions in the limit of infinite dilution obey Raoult's law, i.e.:
:<math> \lim_{X_A \rightarrow 1} P_A = X_A P^*_{v,A} </math>.
[[category: classical thermodynamics]]
[[category: classical thermodynamics]]

Revision as of 19:49, 18 February 2009

Raoult's law states that the vapour pressure of an ideal solution of two components is:

where is the molar fraction of component i, and is the vapour pressure of pure i.

More generally, Raoult's law describes the partial pressure of component A in the vapour coexisting with a liquid mixture as:

.

This law is obeyed for all components of an ideal solution, and is also obeyed for the solvent of an ideal dilute solution. The solute's partial pressure of such solutions then obey Henry's law. Ideal dilute solutions describe the limiting behavior of a mixture of infinite dilution. Therefore, all solutions in the limit of infinite dilution obey Raoult's law, i.e.:

.