Water: Removing dissolved solutes

Precipitation reactions When two solutions are mixed and a solid forms it is called a precipitation reaction The precipitate is the solid formed The solution left over is called the filtrate

Ionic equations When ionic substances dissolve in water, they dissociate into their ions in solution The ions that react to form the precipitate are written in the ionic equation Those ions that do not take part are called spectator ions

Ionic equation Write a balanced equation for the reaction below Write the ionic equation and name the spectator ions

Questions Pg 222 Q 1 and 2

Maintaining water quality Water often needs to be treated before it is consumed by humans Most water in Australia is collected into dams but is not considered fit for human consumption

Treatment of drinking water Most water is treated before coming out of our taps there are several stages of treatment 1.Flocculation Is the process by which small suspended particles in water join together to form larger heavier particles

2. Settling The water is left to stand and the heavier particles then settle which makes the water cleaner The sludge accumulates at the bottom 3. Filtering Water is allowed to filter down through a bed of sand over gravel. This removes all suspended matter 4. Chlorination The main purpose of chlorination is to remove biological contaiminants. Hypochlorus acid kills microorganism

Hard water Hard water is caused by the presence of some metal ions, mainly calcium, magnesium and iron Hard water deposits on the inside of kettles and water pipes In Melbourne we have soft water

Desalination Desalination involves the removal of salts from seawater to obtain fresh water. Because of the lack of fresh water in melbourne we may

Distillation If a salt solution is boiled the water turns to steam and then condenses into another flask

Reverse osmosis Osmosis is the process were water diffuses from a solution of low solute concentration to a solution with high solute concentration

Reverse osmosis Normally the water would move into the salt solution In reverse osmosis the water in the salt is pushed through the semipermeable membrane

Ion Exchange Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex.