Comparison To Raoult's Law
For a dilute solution, the concentration of the solute is approximately proportional to its mole fraction x, and Henry's law can be written as:
This can be compared with Raoult's law:
where p* is the vapor pressure of the pure component.
At first sight, Raoult's law appears to be a special case of Henry's law where kH = p*. This is true for pairs of closely related substances, such as benzene and toluene, which obey Raoult's law over the entire composition range: such mixtures are called "ideal mixtures".
The general case is that both laws are limit laws, and they apply at opposite ends of the composition range. The vapor pressure of the component in large excess, such as the solvent for a dilute solution, is proportional to its mole fraction, and the constant of proportionality is the vapor pressure of the pure substance (Raoult's law). The vapor pressure of the solute is also proportional to the solute's mole fraction, but the constant of proportionality is different and must be determined experimentally (Henry's law). In mathematical terms:
- Raoult's law:
- Henry's law:
Raoult's law can also be related to non-gas solutes.
Read more about this topic: Henry's Law
Famous quotes containing the words comparison to, comparison and/or law:
“In comparison to the French Revolution, the American Revolution has come to seem a parochial and rather dull event. This, despite the fact that the American Revolution was successful—realizing the purposes of the revolutionaries and establishing a durable political regime—while the French Revolution was a resounding failure, devouring its own children and leading to an imperial despotism, followed by an eventual restoration of the monarchy.”
—Irving Kristol (b. 1920)
“The difference between human vision and the image perceived by the faceted eye of an insect may be compared with the difference between a half-tone block made with the very finest screen and the corresponding picture as represented by the very coarse screening used in common newspaper pictorial reproduction. The same comparison holds good between the way Gogol saw things and the way average readers and average writers see things.”
—Vladimir Nabokov (1899–1977)
“The law of God is a law of change, and ... when the Churches set themselves against change as such, they are setting themselves against the law of God.”
—George Bernard Shaw (1856–1950)