Acids Bases And Salts Flashcards
Litmus color acid
Red
Litmus color alkali
Blue
Phenolphthalein alkali
Pink
Phenolphthalein acid
Colourless
Methyl orange acid
Red
Methyl orange alkali
Yellow
Mash reaction
Metal + acid = Salt + hydrogen
This only works for metals above hydrogen in the reactivity series . Reaction gets slower as reactivity decreases
Magnesium and zinc salts are colourless
Iron salts are very pale
Why does aluminium not react
Protected by a layer of aluminium oxide
OASW
Acid + metal oxide = Salt and water
CAWCS
Metal Carbonate + acid = Salt + water + carbon dioxide
Why does calcium carbonate and sulphuric acid not react
Because the reaction occurs initially but forms a layer of insoluble calcium sulphate Around calcium carbonate . The insoluble layer protects the carbonate from further reaction with the acid
BAWS
Base (metal hydroxide) + acid = Salt and water
What are acids
Substances which dissolve in water to form the H+ aqueous ion
Acids only behave as acids when aqueous
What are bases
Substances which react with acids ( combine which h+ ions )
E.g metal oxides , carbonates , hydroxide
What are alkalis
Bases which dissolve in water to form the (OH) - aqueous ion
Most are soluble metal hydroxides
What is neutralisation
Tye reaction of an acid with a base . Whenever acids react they are neutralised resulting in salt formation
What do you use a precipitation method for
To prepare insoluble salts
- Combine two solutions containing one of the two ions required to form the salt
- Filter precipitate
- Wash filter paper with distilled water
- Leave the precipitate in the filter paper to dry
What is titration used for
To prepare soluble salts from an acid and soluble base (potassium , sodium and amonium salts )
A known volume of the acid is measured into a conical flask using a pipette . A few drops of indicator are added . When the indicator changes colour the volume of alkali added from the buttered is recorded . Process is repeated to obtain and accurate average value needed to neutralise the acid then the process is repeated again without the indicator to give a pure salt solution
Go obtain the salt warm gently in an evaporating basin allow half the water to be boiled off and then leave the remained to cool and evaporate forming large crystals
Reaction of an acid with an insoluble base or metal
This is used to prepare soluble salts from an insoluble base
Place appropriate acid in a beaker on the tripod and gauze and warm in a Bunsen burner . Add the insoluble base and stir. It will fizz then add more until all the acid has been neutralised and the base will sink to the bottom Unreacted . Then filter leaving just the salt .
To get a solid salt - warm gently on an evaporating basin on a a tripod on the gauze . Allow half the water to boil off to concentrate the solution then allow the remainder to cool and evaporate forming large crystals
How does hydrogen burn
Forms water
How do you test for water
Turns cobalt chloride paper pink
Water boils at 100degrees
Can you produce an insoluble salt from the reaction between a solid and a liquid
No
All nitrates are
Soluble
All sodium potassium and Amonium are
Soluble
Most common chlorides are …. except
Soluble except lead chloride and silver chloride is
Most common sulfates are ….. except ……
Soluble except leas sulfate , barium sulfate and calcium sulfate
Most common carbonates are …… except …..
Insoluble except potassium amountium and sodium
Most metal hydroxides and oxides are
Insoluble Except sodium postassium ammonium and calcium
What reacts with acid in the cold
Carbonates and magnesium in all others the acid needs to be heated
Why are solutions insoluble
The attractions are so strong the ions clump together and form a solid
