GCSE: salts and more Flashcards
What is a salt?
A salt is a substance formed when the hydrogen ions in an acid are replaced by metal ions.
Do all metals react with acid?
No, they must be above hydrogen in the reactivity series. eg gold is below hydrogen
Are all salts soluble (when are they not)?
all salts are soluble to a certain degree. A salt is classified as insoluble if less than 1g of it dissolves in 1 litre of water.
True or False:
Salts of the Group 1 metals are soluble
True
Are Ammonium salts/nitrates soluble?
yes
What are the exceptions to the rule ‘Chlorides are soluble?’
silver and lead chloride are insoluble
What 3 sulphates are insoluble?
barium, lead and calcium. the rest are soluble
True or False:
Carbonates and oxides are soluble. hydroxides are insoluble no exceptions
False - carbonates, oxides and hydroxides are all insoluble except group 1 and ammonium
What does (aq) mean?
aqueous - dissolves in water (s0luble)
What are the results of the flame tests/
Lithium - red flame
Sodium - orange flame
potassium - lilac flame
callcium - brick red
How to test for cations with sodium hydroxide
Add sodium hydroxide to a solution containing the ions.
Cu2+ ion - blue
Fe3+ ion - orange/brown
Fe2+ - green/dark green
No precipitate but a smell of ammonia = the presence of ammonium ions NH4+ (damp red litmus paper turns blue)
What is the test for halogen ions?
Halogen ions are chlorides, bromides and iodides.
test: Add dilute nitric acid followed by a few drops of silver nitrate solution.
Chloride ions - white precipitate
Bromide ions - pale cream precipitate
iodide ions - yellow precipitate
What is the test for sulphates?
Add dilute hydrocholoric acid to make solution acidic.
Add few drops of barium chloride solution
White precipitate of barium sulphate
What is the test for carbonates?
To carbonate add dilute hydrochloric acid. Bubble gas through lime water.
The gas produced turns lime water from colourless to cloudy
Equation: carbonate + acid - salt + water + carbon dioxide
Complete:
a) acid + base -
b) acid + metal -
c) acid + carbonate -
a) salt + water
b) salt + hydrogen
c) salt + water + carbon dioxide
How to make soluble salts using acids and insoluble bases?
1) Add insoluble base to acide (using burette) - solid will dissolve in acid as it reacts. Use methyl orange indicator to know when the acid has been neutralised (what colour?)
2) Filter out excess base to get the salt solution. Evaporate the water.
How to make a soluble salt using an alkali/
1) You have to add exactly the right amount of alkali to just neutralise the acid
2) Heat and stir the acid and alkali then filter into conical flask
3) Then heat in an evaporating dish
How to make insoluble salts - precipitation reactions?
If the salt you want to make is insoluble you can use a precipitation reaction.
- Pick 2 solutions, containing the ions you need.
Eg. BaCl2 (aq) + H2SO4 (aq) - BaSO4 (s) + 2HCl (aq)
