Solutions And Solubility


Not everything has to dissolve in water. There are many natural occurring substances that cannot dissolve in water such as sand. We know that sand doesn’t dissolve due to the ocean bed is mad up of rocks and sand. But we do know that salt (NaCl) does dissolve, as we can taste a salty taste in the ocean water.

The majority of substances only dissolve in a liquid when both solute and liquid have the same types of molecular forces. I.e. if the solute that is trying to be dissolved and has the same intermolecular forces, then it should by all means dissolve.

Organic Solutions and Liquids

Ethanol and Water

Ethanol has the formula CH3-CH2-OH. The OH group is called a hydroxyl group or alcohol group. This group allows hydrogen bonding to the Water molecules, which have the formula H2O. Both of these substances can possess hydrogen bonding and also there is covalent bonding within both molecules therefore the hydrogen bonding allows ethanol to dissolve in water.

Water and Hydrocarbons

Hydrocarbons tend not to dissolve in water. For example, Hexane (C6H14), which is a liquid, is unable to dissolve in water. This is due to the hydrocarbon chain being unable to interact with waters hydrogen bonding. Instead Hexane possesses a force called Van Der Waals forces. Instead, when mixing both liquids together, it forms layers, separating each liquid by weight (denser on the bottom). These liquids when mixed are generally called immiscible.

Ionic Solids in Solutions

Salt and Water

Sodium Chloride (NaCl) is a solid. NaCl is has the ability to dissolve in water, but it doesn’t possess hydrogen bonding. The only reason it is able to dissolve is due to Sodium Chloride being a ionic solid. It is able to undergo lattice dissociation so the NaCl becomes Na+(aq) and Cl-(aq).

Water molecules are polar molecules resulting in a slight overall charge causing attractions to the ions in the giant ionic lattice. The partial positive charge on the hydrogen is attracted to the Cl ion, which has a negative charge. Where the partial negative charge on the oxygen is attracted to the Na ion, which has a positive charge. This action results in the water molecule pulling the ions away from the lattice causing the ionic solid to dissolve.

Increasing Solubility of Ionic Solids

Ionic solids can be influenced by two factors. These are: - Charge of the lattice ion; and - Ionic Radius.

1. If the charge of the lattice ion is small, there is less overall attractive forces holding the lattice together so less energy is required to separate the ions form the lattice.

2. If the ionic radius is bigger, the ions in the lattice are unable to approach each other as closely therefore their interactions are smaller and the bonds are easily broken.

Recovery of Ionic Solids (Salts) From Solution

The solubility of a solute is dependant upon temperature. In liquids and solids, the general solubility increases as the temperature increases just like adding sugar to tea. There are many practical techniques that allow us to recover salts from a solution, which rely on temperature.


Evaporation of a solution is able to remove enough energy from the system so the lattice can reform.


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