Editing Raoult's law (section)

===Negative deviation=== 
[[File:Raul minus.jpg|thumb|upright|Negative deviation from Raoult's law]]

When the adhesion is stronger than the cohesion, fewer liquid particles turn into vapor thereby lowering the vapor pressure and leading to negative deviation in the graph.

For example, the system of [[chloroform]] (CHCl<sub>3</sub>) and [[acetone]] (CH<sub>3</sub>COCH<sub>3</sub>) has a negative deviation<ref>P. Atkins and J. de Paula, ''Physical Chemistry'' (8th ed., W. H. Freeman 2006) p. 146.</ref> from Raoult's law, indicating an attractive interaction between the two components that have been described as a [[hydrogen bond]].<ref>{{cite journal |last1=Kwak |first1=Kyungwon |last2=Rosenfeld |first2=Daniel E. |last3=Chung |first3=Jean K. |last4=Fayer |first4=Michael D. |date=6 November 2008 |title=Solute-Solvent Complex Switching Dynamics of Chloroform between Acetone and Dimethylsulfoxide Two-Dimensional IR Chemical Exchange Spectroscopy |journal=J. Phys. Chem. B |volume=112 |issue=44 |pages=13906–13915 |doi=10.1021/jp806035w |pmc=2646412 |pmid=18855462 |citeseerx=10.1.1.560.3553 }}</ref> The system HCl–water has a large enough negative deviation to form a minimum in the vapor pressure curve known as a (negative) [[azeotrope]], corresponding to a mixture that evaporates without change of composition.<ref>Atkins and de Paula, p. 184.</ref> When these two components are mixed, the reaction is exothermic as ion-dipole intermolecular forces of attraction are formed between the resulting ions (H<sub>3</sub>O<sup>+</sup> and Cl<sup>–</sup>) and the polar water molecules so that Δ''H''<sub>mix</sub> is negative.