Salts Noadswood Science, 2012

Wednesday, April 26, 2017 Salts To know what salts are

Salts Salts are extremely useful chemicals There are many different salts which can be produced, and their uses are vary varied… They are produced when a neutralisation reaction occurs Acid Alkali Salt + Water

Making Salts If the base dissolves in water just enough acid needs to be added to make a neutral solution followed by evaporation of the water Larger crystals form if you evaporate the water slowly

Making Salts Copper oxide, and other transition metal oxides or hydroxides, do not dissolve in water If the base does not dissolve in water it must be added to the acid until no more will dissolve and there is some base left over (excess) The mixture must then be filtered to remove the excess base, and evaporated to leave the salt behind…

Experiment You are going to mix an acid (hydrochloric acid) and an alkali (potassium hydroxide) causing a neutralisation reaction Potassium chloride is the salt produced Acid + Alkali → Salt + Water Hydrochloric acid + Potassium hydroxide → Potassium chloride + water

Experiment – Part I Add 25cm3 hydrochloric acid to a 100cm3 beaker Add 2cm3 potassium hydroxide solution and stir Measure the pH using UI paper Repeat steps 2 and 3 until the mixture is no longer acidic *Record how much alkali you had to add!

Experiment – Part II Now add your mixture into an evaporating basin, and heat gently Heat until there is about a third of the liquid left (do not let it boil dry, as it will spit hot crystals out) Examine the salt found

What Salt? Different salts are produced from different acids Hydrochloric acid makes a metal chloride Sulphuric acid makes a metal sulphate Nitric acid makes a metal nitrate Phosphoric acid makes a metal phosphate

Naming Salts The name of a salt has two parts. The first part comes from the metal in the base or carbonate, or the metal itself if a reactive metal like magnesium or zinc is used The second part of the name comes from the acid used to make it. The names of salts made from hydrochloric acid end in -chloride, while the names of salts made from sulfuric acid end in -sulfate

Naming Salts Metal Acid Salt Sodium hydroxide Reacts with Hydrochloric acid To make Sodium chloride Copper oxide Copper chloride Sulfuric acid Sodium sulfate Zinc oxide Zinc sulfate

State Symbols State symbols describe the physical state something is in… Solid (s) Liquid (l) Gas (g) Aqueous – dissolved in water (aq)

Salt uses Salts can be put to many uses, including: - Fertilisers (calcium phosphate & potassium nitrate) Preservatives (sodium chloride) Gun powder (potassium nitrate) Varnish (copper sulphate) Dye (copper sulphate) Photographic film (silver nitrate)

Worksheet Complete the worksheet about salts