Chemical Changes Flashcards
(28 cards)
Reactivity series
Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
Platinum
Acid
A chemical which tastes sharp, is corrosive and releases hydrogen ions into the water
Alkali
A base which is corrosive, is used in soap and release’s hydroxide ions in water
Base
A chemical which neutralises acid but does not necessarily dissolve in water
Salts
Made up of two ions in an ionic compound usually one metal and one non metal
Metal + acid
Metal + acid —> salt + hydrogen
Acid + alkali
Acid + alkali—> salt + water
Acid + base
Acid + base —> salt and water
Acid + metal carbonate
Acid + metal carbonate —>salt + CO2 + water
Pure dry sample of a soluble salt from an insoluble oxide or carbonate
Add 50 cm3 dilute acid into a beaker and warm gently using a Bunsen burner
Add the insoluble oxide slowly to the hot dilute acid and stir until the base is in excess (i.e. until the base stops dissolving and a suspension of the base forms in the acid)
Filter the mixture into an evaporating basin to remove the excess base
Gently heat the solution in a water bath or with an electric heater to evaporate the water and to make the solution saturated
Check the solution is saturated by dipping a cold glass rod into the solution and seeing if crystals form on the end
Leave the filtrate in a warm place to dry and crystallise
Decant excess solution and allow the crystals to dry
Why excess zinc not iodine
1 insoluble base
2 can be removed through filtration
3 pure crystals when iodine is fully reacted
Dm3 <—> Cm3
Dm *1000 —> cm3
Cm3 /1000 —> dm3
Conc triangle
Mass/mol = volume * concentration
When is electrolysis used
When an element is more reactive than carbon
Electrolyte
A liquid which conducts electricity
Molten electrolysis
What is formed at the anode and cathode
Anode - non Metal
Cathode - metal
Molten electrolysis
Reduction or oxidation at anode and cathode
Anode - oxidation
Cathode - reduction
Why must the ionic compound be dissolved or molten
To allow the IONS to move
What is added to aluminium (molten)
Why
Cryolite
To lower the melting point
Why must the anode be replaced regularly
It burns off as it reacts with the oxygen on its surface to form CO2
Electrolysis in solutions
+ ions at cathode
Metal+ and H+ ions
The reactant LOWER in the reactivity series is discharged
Electrolysis in solutions
- ions at anode
?ion- and OH- ions
Halogen is always discharged if present
If not OH is discharged
Halogens discharged in pairs
Aluminium extraction locations and costs
1 near transport links
Near raw materials
Near a cryolite source
2 cost of shipping
Cost of heating
Aluminium reaction
