Solubility and salt preparation Flashcards
- What is a solvent?
A liquid that a solute dissolves in
- What is a solute?
A solid that dissolves in a solvent
- What is a solution?
The mixture produced when a solute is dissolved in a solvent
- What is a saturated solution?
The maximum mass of solute that can dissolve in a solvent for a given temperature
- How does solubility increase with temperature?
Solubility increases with temperature, the higher the temperature, the more solute can be dissolved
How is solubility measured?
In [mass] (g)/100g [liquid solute is dissolving in]
Solubility rules
Halides (iodides, chlorides, bromides) Soluble except lead (Pb) and silver (Ag) halides
Hydroxides and oxides (OH) Insoluble except group 1 and ammonium
Sulfates (SO4) Soluble except barium (Ba) and calcium (Ca)
Group 1 and ammonium (NH4) Always soluble
Carbonates (CO3) Insoluble except group 1 and ammonium (calcium carbonate is slightly soluble in water)
Nitrates Always soluble
Formulae of sulphate ions
SO4 2-
Formulae of nitrate ions
NO3 -
Formulae of carbonate ions
CO3 2-
Formulae of hydroxide ions
OH-
Formulae of sulphuric acid
H2SO4
Formulae of nitric acid
HNO3
Formulae of Hydrochloric acid
HCL
Formulae of ammonia
NH3
Formulae of ammonium
NH4+
Formulae of lead ion
Pb 2+
Formulae of hydrogen ion
H +
Formulae of silver ion
Ag +
Formulae of zinc ion
Zn 2+
What is an acid?
A donor of H+ ions (HCl, HNO3, H2SO4)(CH3COOH – ethanoic acid)
What is a base?
A source of OH- ions that reacts with an acid
What is a salt made up of?
A metal bromide/nitrate/sulfate/iodide/chloride
What happens when two salt solutions are mixed together that produce soluble salts ?
There is no reaction as the products of the reaction are both soluble, so ions diffuse around the solution
What is a precipitate?
An insoluble solid that is produced in a precipitation reaction
How are precipitates formed?
By precipitation reactions
Two soluble salts react to make an insoluble salt and a soluble salt
What can and cannot be made using a precipitation reaction?
Soluble salts cannot be made using the precipitation reaction
They would be made using the copper(II)sulfate method that starts from an acid and an alkali
Example: copper(II)oxide + sulfuric acid —> copper(II)sulfate + water
Insoluble salts can be made using the precipitation reaction
Soluble salt + soluble salt —> insoluble salt + soluble salt
How is a pure, dry sample of an insoluble salt prepared?
- Mix solution of two soluble reactants
- Filter mixture (insoluble salt will remain on filter paper)
- Wash the salt with distilled water (makes sure the sample is pure)
- Leave the salt to dry
Rules when writing ionic equations
Write out a balanced symbol equation
Ionic compounds (soluble), acids and bases dissociate (split up)
Cancel out terms that appear on both sides of the equation (spectator ions)
Substances that do not dissociate do not become charged (eg H2)
What types of compounds are usually coloured?
Transition metal compounds
Copper(II)sulfate colour
Light blue solution
Lead(II)nitrate colour
Colourless solution
Iron(III)chloride colour
Yellow solution
Table recording results of precipitation reactions practical with colour changes
Copper(II)sulfate + potassium iodide
Light blue solution to red-brown precipitate
Copper(II)sulfate + sodium hydroxide
Bright blue precipitate (gelatinous appearance) formed in light blue solution
Copper(II)sulfate + potassium sulfate
No change - stayed a light blue solution
Lead(II)nitrate + potassium iodide
Colourless to opaque bright yellow precipitate
Lead(II)nitrate + sodium hydroxide
White preciptate formed from colourless solution
Lead(II)nitrate + potassium sulfate
No colour change – stayed a colourless solution
Iron(III)chloride + potassium iodide
No colour change – stayed a yellow solution
Iron(III)chloride + sodium hydroxide
Iron(III)chloride + potassium sulfate
No colour change – stayed a yellow solution
