Chapter 11 Acids and Bases - Making salts/Salt prep Flashcards
4 ways of making salts
reacting acids with:
(a) an alkali by titration
(b) excess metal
(c) excess insoluble base
(d) excess insoluble carbonate
Process to make a salt if you start with a metal
what type of salt is made
soluble salt
Add excess of the metal to the acid. It starts bubbling. When the bubbling stops all the acid is used up.
Filter the excess metal
Heat the solution to evaporate some water and obtain a saturated solution.
Do glass rod test to see when solution is saturated
When the saturated solution is left to cool, the salt crystal appears
filter the crystallized salt
Dry with filter paper or in an oven
What metals can you start with to make salts
Magnesium, aluminium, zinc and iron
Process of making salt if you start from an insoluble base or insoluble carbonate
what is this method generally used for
what type of salt is formed
Add insoluble base in excess to the acid acids until it completely neutralized
Remove excess insoluble base by filtration
Heat solution to evaporate osme water and obtain a saturated soltuion
Leave to cool until crystals of the salt form
Filter the crystalized salt
Dry with filter paper or in an oven
Generally used to prepare copper salts. Even copper carbonate uses the same method
soluble salt is formed
Process of making salt if you have dilute acid and alkali
which type of salt is formed
soluble salt is formed
Carry out titration first: add 25 cm3 of the standard solution or unkown solution (acid or alkali) into a flask using a pipette
Add an indicator
Add the other solution (acid or alkali) from a burette one drop at a time. Swirl the flask carefully.
When the solution is neutral stop adding the other Solution
Record how much of the solution was required for neutralization and carry out process again without the indicator (impurity)
Heat the solution from the flask to evaporate the water. Crystals of salts are left behind.
Process of making salts by precipitation
what type of salts are made from precipitation
insoluble salts are made
Make separate solutions, one containing the cation and the other containing the anion of the desired salt
Mix them. A white or coloured precipitate is formed
Filter the mixture, the residue is the precipitate
Rinse the precipitate by running distilled water through it
Place the precipitate in a warm oven to dry
What is a precipitate
Insoluble product that is formed upon mixing reactants
What are hydrated salts
Salts with water molecules chemically bonded to the crystals
How to write chemical formula of hydrated salts
eg
Salt . xH2O
x = ratio of water molecules to salt molecule
eg
CuSO4 . 5H2O
for every CuSO4 molecule there are 5 water molecules
What is water of crystallisation
It is the water bonded into the hydrated salts
What are anhydrous salts
Salts where the water has been driven off by heating
but when the salt cools, water molecules from the environment will be taken in again from the surroundings.
Why is it necessary to filter the mixture after mixing and stirring
to remove residue
why is it necessary to wash the precipitate underwater
to remove soluble impurities
chlorides, bromides, iodides soluble or insol
most are soluble
only lead and silver halides are insoluble
are nitrates soluble or insoluble
all nitrates are soluble
