Chemical Changes Flashcards
Neutralisation
A reaction between an acid and a base to produce a salt and water
Acid
A substance with a pH of less than 7
The higher the concentration if the ion, the more acidic a substance is
Base
A substance that reacts with an acid to produce a salt and water
Alkali
A base that is soluble in water
The higher the concentration of hydroxide ions, the higher the pH
What are the indicators of pH?
Litmus - red - acidic purple - neutral blue- alkaline
Methyl orange/red -acidic yellow- neutral and alkaline
Phenolphthalein - colourless- acidic+ neutral pink- alkaline
Acid ionising
All acids can ionise in a solution - split into H+ ions and other ion
Strong acids
Completely dissociate in water
Completely ionise in water
They have a low pH of 0-2
Weak acids
Only partially dissociate in water
Do not fully ionise
pH is around 6
What is ionisation of a weak acid!
A reversible reaction - sets up an equilibrium
Concentrated
An acid with a large number of acid molecules compared to the volume of water
How many particles are dissolved in a given volume of liquid
Dilute
A small number of acid molecules compared to the volume of water
If a concentration of H+ ions increase by a factor of 10…
The pH decreases by 1
If the H+ concentration increases by a factor of 100…
The pH decreases by 2
Acid + metal oxide
- salt and water
Acid + metal hydroxide
Salt + water
Acid + metal
Salt + hydrogen
Acid + metal carbonate
Salt + water + carbon dioxide
Soluble rules in water
Chlorides
Sulfates
Nitrates
Sodium, potassium, ammonium hydroxide, carbonate
Insoluble in water rules
Silver,lead chloride
Lead, barium, calcium sulfate
Most carbonates
Most hydroxides
How do you make insoluble salts
Add two soluble salts to make insoluble salt
The more H+ ions an acid has…
The lower the pH - 1/2
The less H+ ions in an acid…
The higher the pH - 4/5
Strong acids
Sulphuric acid
Hydrochloric acid
nitric acid
Weak acid
Ethanoic acid
Citric acid
Carbonic acid
Method for lead nitrate + sodium chloride - lead chloride +sodium nitrate
Add lead nitrate to test tube + add deionised water
Add sodium chloride to another tube and water
Mix together - lead chloride should precipitate out
Filter solution - scrape lead chloride onto filter paper
How do you make a soluble salt?
React an acid with an insoluble salts
Making soluble salts method
Sulphuric acid and copper oxide
Add base to a liquid
Filter off the excess solid
Evaporate the water
Allow to cool and allow salt to crystallise
Titration method
Pipette and filler - transfer 25cm of aqueous sodium hydroxide into flask- add drop of phenopeliain - close tap on burette -fill hcl
Record initial burette reading from meniscus
Add hcl to sodium hydroxide - mix gently
Record final burette reading - calculate titre and repeat 3 times
Electrolytes
A molten or dissolved ionic compound
Electrolysis
The breaking down of a substance using electricity
An electric current is passed through an electrolyte causing it to decompose
Positive ions in electrolysis
Cations in the electrolyte move towards the cathode -negative electrode- and are reduced - gain electrons-
Negative ions in electrolysis
Anions in the electrolyte move towards the anode -positive electrode- are oxidised - lose electrons
This creates a flow of charge through the electrolyte
Why can’t an ionic solid not be electrolysed?
The ions are in a fixed position and can’t move
Why can molten ionic compounds be electrolysed?
The ions can move freely and conduct electricity
Predicting products of electrolysis- positive metal ions
Reduced to metal atoms at the cathode
Predicting products of electrolysis - negative metal ions
Oxidised to atoms at the cathode
MASH
Metal + Acid — Salt + hydrogen
BASHO
Base + Acid — Salt + Water
CASHOCO
Carbonate + Acid — water+ carbon dioxide
Examples of base
Any metal followed by oxide or hydroxide
