2.1 “Like Dissolves Like”
Some substances readily dissolve in a liquid while others do not. One rule of thumb is “like dissolves like” and refers to the intermolecular forces that the solute and solvent exhibit. For example, water readily dissolves sucrose (it is miscible) as both can form hydrogen bonds.
Figure 2.3: Sucrose can form hydrogen bonds and readily dissolves in water.
Water and oil do not readily mix (it is immiscible) as water forms hydrogen bonds whereas hydrocarbons exhibit dispersion.
Figure 2.4: Octane, found in petroleum products, is dispersion dominated and does not readily dissolve in water.
Intermolecular forces can help us predict if one substance will be soluble in another.
![Favorable interactions for dissolving [@tro2017]](files/ch11/imf-dissolve.png)
Figure 2.5: Favorable interactions for dissolving3
Solutions are usually liquid but can be a solid or gas.
| Solution | Solute | Solvent |
|---|---|---|
| air | O2(g) |
N2(g) |
| soft drinks | CO2(g) |
H2O(l) |
| palladium hydride | H2(g) |
Pd(s) |
| rubbing alcohol | H2O(l) |
C3H8O(l) |
| saltwater | NaCl(s) |
H2O(l) |
| brass | Zn(s) |
Cu(s) |