2 7 acids bases and salt preparations

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

True. Sodium carbonate is soluble.

True. Compounds of potassium are soluble.

False. Compounds of sodium are soluble.

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

Three examples of insoluble sulfates are:

The chemical name for limewater is calcium hydroxide.

False. All nitrates are soluble.

Examples of soluble hydroxides include:

False. Silver chloride is insoluble.

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

An acid is a proton donor.

In solution, an acid ionises, producing protons (H+ ions), making the solution acidic.

A base (alkali) is a proton acceptor.

In solution, a base ionises, producing hydroxide ions (OH-) which can accept protons, making the solution alkaline.

True. Acids and bases are involved in proton transfer.

An aqueous solution becomes acidic due to the presence of protons (H+ ions) released by acids.

The general equation for the reaction between a metal and acid is: metal + acid ⟶ salt + hydrogen

False. Only metals above hydrogen in the reactivity series will react with dilute acids.

The general equation for the reaction between an acid and a base is: acid + base ⟶ salt + water

A neutralisation reaction is a reaction between an acid and a base to form a salt and water.

False. Effervescence is produced when an acid reacts with a metal carbonate, due to the formation of carbon dioxide gas.

The products formed from the reaction between sodium hydroxide and hydrochloric acid are sodium chloride and water.

The general equation for the reaction of a metal carbonate with an acid is: metal carbonate + acid ⟶ salt + carbon dioxide + water

The word equation for the reaction between sodium carbonate and sulfuric acid is: sodium carbonate + sulfuric acid ⟶ sodium sulfate + water + carbon dioxide

The identity of the salt produced depends on the acid used and the positive ions in the base.

Metal oxides, metal hydroxides and metal carbonates act as bases in acid-base reactions.

A base that is water-soluble is referred to as an alkali. All alkalis are bases, but not all bases are alkalis.

Alkalis have pH values above 7.

Bases are usually oxides, hydroxides, or carbonates of metals.

When ammonia reacts with water, it produces hydroxide ions.

In basic (alkaline) conditions, red litmus paper turns blue.

True. Aqueous ammonia and ammonium hydroxide are the same thing.

The hydroxide, OH-, ion is produced in alkaline solutions.

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.

Phenolphthalein is colourless in acids and pink in alkalis.

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.