7 2 preparation of salts

A soluble salt can be made by the reaction of:

The insoluble base is added in excess to ensure that all of the acid has reacted.

The excess insoluble base is removed by filtration.

After removing the excess base, only the salt and water remain in the solution.

The balanced symbol equation is: CuO (s) + H2SO4 (aq) ⟶ CuSO4 (s) + H2O (l)

An insoluble base is a base that does not dissolve in water.

The solution is heated gently and then left to cool.

The method used to prepare a soluble salt from an acid and alkali is titration.

The piece of equipment which could be used to measure a fixed volume of acid is a pipette.

An indicator will indicate when neutralisation has occured.

True. During the preparation of a soluble salt by titration, the titration is repeated without the indicator.

An insoluble salt is a salt that does not dissolve in water or other solvents.

True. Insoluble salts can be prepared using a precipitation reaction.

A precipitation reaction is a reaction where an insoluble solid (precipitate) is formed from two soluble reactants

A precipitate is an insoluble solid that is formed from a reaction between two soluble reactants.

The method for preparing an insoluble salt involves measuring out a fixed volume of one solution and then adding the second salt solution until it is in a slight excess, to ensure the maximum amount of precipitate will be obtained.

False. The precipitate is recovered by filtration and then it must be washed with distilled water to remove reactants that are contaminating the residue (recovered solid).

Examples of salts made by precipitation include silver and lead(II) salts e.g. lead(II) iodide, silver chloride.

The precipitate is washed with distilled water to remove traces of the solutions it was made from.

An ionic compound consists of a giant lattice of positively charged metal ions and negatively charged non-metal ions.

Insoluble means the substance is unable to dissolve in a solvent, usually water.

False. Not all ionic compounds are soluble in water, some are insoluble.

True. Sodium carbonate is soluble.

True. Compounds of potassium are soluble.

False. Compounds of sodium are soluble.

Three examples of insoluble sulfates are:

False. All nitrates are soluble.

Examples of soluble hydroxides include:

False. Silver chloride is insoluble.

A hydrated substance is one which is chemically combined with water.

An anhydrous substance is a substance containing no water.

Water of crystallisation refers to the water molecules present in a hydrated substance.

True. ** The formula of hydrated copper(II) sulfate is CuSO4∙**5H2O.

The formula of hydrated cobalt(II) chloride is CoCl2∙6H2O.

The formula of anhydrous copper(II) sulfate is CuSO4.

When hydrated copper sulfate is heated the colour change is blue to white and colourless liquid (water) collects at the top of the test tube.

The equation for the reversible reaction when copper(II) sulfate is heated is: CuSO4.5H2O ⇌ CuSO4  +  5H2O

Anhydrous copper(II) sulfate turns blue in the presence of water.

There are 6 water molecules present in CoCl2∙6H2O.

The formula of anhydrous cobalt(II) chloride is CoCl2.