Solubility

Solution

A clear, homogenous mixture consisting of a solute and solvent

Solvent

The major component of a solution, by mass

Solute

The minor component(s) of a solution, by mass

Solubility

How much solute can be dissolved in a specific mass of solvent at a specific temperature

Rule for gas solubility

As temperature increases, less gas can be dissolved by a constant volume of solvent

Saturated solution

A solution that has dissolved the maximum mass of solute it can for that temperature and mass of solvent.

Unsaturated Solution

A solution that has less mass of solute dissolved than it could at that temperature and mass of solvent.

Supersaturated Solution

A solution that has dissolved the more than maximum mass of solute it can for that temperature and mass of solvent. This can be achieved by lowering the temperature of a saturated solution, however is unstable and it is likely that the excess solute will crystallise/precipitate out of solution.

Electrolytes

Substances (e.g. ionic compounds [always strong]), that form ions when dissolved in water.

They can be strong (entirely ionises, e.g. NaCl, Ca(NO₃)₂, HCl) or weak (partially ionises e.g CH₃COOH, H₂S, H₂CO₃).

Conductivity of water

Electrolytes are so called because the mobile ions allow water to conduct electricity.

Pure water does not conduct electricity, as water dissolves a greater number of ions, its ability to conduct electricity increases.

Thus, strong electrolytes produce the most conductive water, followed by weak.

Non-electrolytes do not allow water to conduct electricity.

Non-electrolytes

Substances that exist only as molecules when dissolved in water, e.g. O₂, I₂, CS₂

Dissociation

Ions in an ionic compound are released and become mobile in an aqueous solution

Ionisation

A reaction between electrolyte molecules (e.g. HCl, H₂SO₄, HNO₃) and water, that forms ions not originally present in the substances.

Solvation

The attraction of polar solvent molecules to the ions of an ionic solid.

Hydration

Solvation by water (highly polar due to hydrogen bonds, which leads to ion-dipole forces that can overcome the ionic bonds of ionic solid solutes)

Precipitation Reaction

Formation of a solid precipitate from a solution.

Suspension

A heterogenous mixture of small precipitate particles that have not settled to the bottom of the container, giving the mixture a cloudy appearance.

Concentration

qty of solute / qty of solution

Potable water

Clear, tasty, colourless, odourless, pathogen and toxin free water

Reverse Osmosis

A process for purifying water with high TDS (impurities), involving using pressure to force water through a semipermeable membrane that blocks ions, pathogens, and large molecules while allowing water through. This process creates distilled water known as permeate.

Why is water fluoridated?

To reduce tooth decay

What is the permissible pH for tapwater in Australia?

6.5-8.5

Why is water monitoring important?

It ensures that our water supply is safe for consumption, ie not contaminated by pathogens or heavy metals (toxic/carcinogenic)