A1 Relating Properties To Uses And Production Of Substances Flashcards
Oxide
Any atom that is bonded with an oxygen eg carbon monoxide, magnesium oxide, ion oxide
Acid
Contains a hydrogen and dissociates in water to form hydrogen ion
A base
A substance that will react with acid to form salt and water
Alkali
A base that dissolves in water
Sodium hydroxide uses
- To make plastics and soap
- used as drain cleaner
Calcium hydroxide uses
- used to raise ph of acidic soil by farmers
- used in the treatment of acidic waste from factories that produce sulfuric acid
Sulfuric acid and calcium hydroxide neutralisation reaction equation
H2SO4 + Ca(OH)2 = CaSo4 + 2H2O
Magnesium hydroxide
To treat stomach acid indigestion
Amphoteric
Substance that can act as an acid or base in hot conditions
Aluminium oxide (amphoteric) uses
- filler
- paint
- glass
Transition metal definition
A metal that forms an ion with a partially filled d subshell.
Name the process and catalyst (transition metal)
The Haber process. Fe is the catalyst
Transition metals function
- they form coloured solutions
- they are good catalysts as they can accept or donate electrons
- form complex ions
Complex ion
Central atom or ion surrounded by ligands
Ligands
Substance that can donate a lone pair of electrons and form a coordinate bond eg lone pairs of electrons from oxygen donated to vanadium.
How catalysts happen
- adsorption:reactants stick to the surface of the active site of the catalyst
- the reactant bonds weaken
- reaction occurs between the reactants
- desorption: as the products form they are released from the catalyst surface
What is the catalyst in the contact process?
Vanadium oxide - v2O5
Explain why transition metals can act as catalysts
- they have partially filled d subshells
- can accept or lose electrons which means they can be oxidised or reduces
- so it provides an alternative pathway for a reaction with a lower activation energy
How does a catalyst lower the amount of energy needed for a reaction
- adsorbs onto the surface by weakening the bonds
- as electrons are accepted and donated back
- this provides an alternative pathway for a reaction with lower activation energy
- so collisions with less energy will react
Steps in the Bayer process
1) bauxite ore is crushed to form grains to increase the rate of reaction
2) it is then reacted with hot sodium hydroxide under pressure (as al2o3 is amphoteric and can react with alkaline NaOH)
3) this then forms a slurry
4) alumina dissolves but iron oxide doesn’t (as al2o3 is acidic so will dissolve however iron oxide is alkaline so will not react with NaOH)
5) impurities are filtered off
6) solution is then cooled and seeded with aluminium oxide (to form smaller crystals which will grow into larger
7) aluminium hydroxide then filtered off then heated in kiln to form alumina.
Electrolysis
- decomposition of a compound using electricity
- electrolysis can break down Ionic compounds
- the ions must be free to move for it to work
- ionic compounds need to be molten or dissolved
Electrolysis for aluminium extraction
- al2O3 will need to be melted first so that the ions are free to move around during electrolysis
- as al2o3 has high melting point a lot of energy is required and is expensive to melt
- instead it is dissolved in cryolite (al compound with lower melting point) so that the ions are free to move
- positive aluminium ions move to the negative cathode to receive electrons (reduced to Al) al3+ + 3e- = al
- the negative oxygen ions move to positive anode, lose electrons and are oxidised to oxygen gas 2O2- = O2 + 4e-
- the oxygen reacts with the carbon from positive electrodes and forms carbon dioxide, so they gradually burn away. The positive electrodes need to be replaced frequently.
Electrolysis of molten sodium chloride
- the negative chloride ions move to positive anode where they lose electrons to form chlorine gas 2cl- = cl2 + 2e- (oxidation)
- the positive sodium ions move to negative cathode where they gain electrons to form sodium na+ + e- = na
Electrolysis of aqueous sodium chloride
- negative chloride ions move to positive anode where they lose electrons to form chlorine gas 2cl- = cl2 + 2e-
- positive hydrogen ions move to negative cathode and gain electrons to form hydrogen gas 2h+ + 2e- = h2
- as hydrogen more reactive than sodium, Na ions react with OH- ions to form NaOH: na+ + OH- = NaOH
