alkalis , bases and salts

year 10

which compounds are always soluble?

N - nitrates

A - ammonium salts

P - potassium salts

S - sodium salts

which compounds are mainly soluble?

chlorides ( except - agcl and pbcl) - sulphates ( except BaSO₄, CaSO₄, PbSO₄)

what compounds are sometimes insoluble

Hydroxides

Insoluble, except Na⁺, K⁺, Ca²⁺ (Ca(OH)₂ slightly soluble)

acid + proton in terms of protons

acid = proton (H+) donor

base= proton (H+) acceptor

acid + metal

salt + hydrogen

acid + base

salt + water

acid + metal carbonate

salt + water + carbon dioxide

Acids to remember:

• HCl → chloride salts

• H₂SO₄ → sulfate salts

• HNO₃ → nitrate salts

Alkalis

bases that are soluble in water

making a soluble salt from an insoluble base what is the reaction called and what does the base react with?

the base reacts with acid , neutralisation

are metal oxides typically bases or acids?

they are typically bases ( insoluble in water)

what substance has excess hydrogen ions when dissolved in water?

acids

what is the equation when forming a soluble salt from insoluble base

acid + insoluble base = salt + water

what are the steps to form a soluble salt from an insoluble base ?

1 - add the acid to a beaker , add the salt in excess with a spatula ( adding it in excess ensures all the acid is reacted)

2- put the beaker into a warm water bath ( the warmth acts as a catalyst to speed up the rate of reaction)

3 - once the reaction is complete ( when it is between copper oxide and sulfuric acid, you will see a blue solution which is the copper sulphate solution and at the bottom , the insoluble copper oxide)

4- filter the solution to ensure the salt is pure ( the filtrate)

5- put the filtrate into an evaporating dish over a beaker of water + bunsen burner to speed up the rate of water evaporation

6- leave the evaporating dish to cool to slowly evaporate the water for a few days ( the slower the evaporation , the larger the crystals formed) - this will ensure your salt is concentrated and has no water

why are acids soluble in water?

as the acids hydrogen molecules bond with the waters hydrogen molecules, allowing the acid to dissolve and create an acidic solution

how to make a soluble salt by reacting an alkali and acid

1- titration , carry out titration and record the amount of acid needed for the solution to turn light pink

2- repeat with same amount of both substances without the indicator ( this ensures we produce a pure salt and also not a pink salt)

3- then evaporate in water bath

4- leave evaporating dish to cool to ensure no excess water Is left

how to obtain an insoluble salt from two soluble solutions

by precipitation - add the same amount both soluble solutions to a test tube

2- once reacted , the products will be a soluble solution and an insoluble solid

3- filter the solution , remove the residue which is the insoluble solid

4- rinse the insoluble solid with distilled water ( use distilled water as it has no ion impurities)

5- pat down dry