Oxidation and reduction Flashcards
list the three ways of looking at oxidation and reduction
addition or removal of oxygen
transfer of electrons
oxidation number
what are oxidtion reactions defined as
in terms of addition or removal of oxygen
Gaining oxygen
what are reduction reactions defined as
in terms of addition or removal of oxygen
loss of oxygen
what is reduction
In terms of oxygen
the removal of oxygen or the addition of hydrogen
Displacement reaction of metal oxides
in terms of addition or removal of oxygen
a more reactive metal will displace a less reactive metal from a compound
describe the thermite reaction
produce:white hot molten iron in remote locations.
alminium + Iron(III)oxide -> Iron + aluminium oxide
Alminium removes oxygen from iron oxide. The iron is reduced. Alminium is oxidised
What is a displacement reaction of solutions
in terms of addition or removal of oxygen
A more reactive metal will displace a less reactive metal from a solution of one of its salts
Name an example of a displacement reaction
in terms of addition or removal of oxygen
Magnesium + copper(II) sulfate -> copper + magnesium sulfate.
The blue colour of the copper fades as its being used up.the copper metal begins to form.
What is oxidation of an element
In terms of electron transfer
oxidation of an element takes place when it loses electrons
what is reduction of an element
In terms of electron transfer
reduction of an elemnet takes place when it gains electrons
Why do oxidation and reduction reactions occour together
In terms of electron transfer
When one reactant loses electrons the other has to gain electrons
Describe the Zinc and copper sulfate reaction
oxidation and reduction takes place.zinc becomes covered with a reddish deposit which is the copper metal.The blue colour of the solution fades-which implies the copper metals are being used up.This is a redox reaction and a displacement reaction.
What is a redox reaction
a reaction where oxidation and reduction occour simultaneously.( one cannout occour without the other)
an oxidation agent
substance that brings about oxidation in other substances
an reducing agent
substance that brings about reduction in other substances
What is oxidation number
the charge that an stoms has or appers to have when electrons are distrubuted according to certain rules
what is electronegativity
the force of attraction that an atoms has for a shared pair of electrons
What is oxidation
in terms of ON
increase in oxidation number
what is reduction
in terms of ON
decrease in oxidation number
oxidation number rules that have an expection
oxygen oxidation number is always(-2).
expect in peroxides(bonded with hydrogen)
expect with a more electronegative element.
Hydrogen ON number is always +1
expect in metal hydrites where its -1
halogens ON is always -1
expect bonded to a more electronegative element
What is transition metal
an element that forms at least one ion with a partially filled d sublevel
Physical properties of transition elements
good conductors of heat and electricity
hammered or bend into shape easily
high melting points
hard + tough
high densities
chemical properties of transition elements
less reactive than alkali metals
form coloured ions of different charges
some are very unreactive
many used as catlysts
applications of oxidising agents
hyprogen peroxide (H2O2) used to bleach hair
( coloured pigment + H2O2-> colourless hair pogment + H2O
chlorine in swimming pools.Cl2 is oxidising agent
household bleaches. Sodium hypochloride (NaClO)
describe the reactions of the halogens
Reaction with hallides-compared to other halogens
the halogens are very reactive elements and cannot exist in a uncombined form. They act as oxdising agents (take an electron from another element)
clorine is the strongest non dangerous element. Its capable of releasing bromine and iodine form a solutions of its salts
F>Cl>Br>I>At
What is the colour of Chlorine in water
Pale green
What is the colour of Bromine in water
Yellow/ orange
What is the colour of Iodine in water
Brown/red
What is the colour of Chloride ions in water
Colourless
What is the colour of Bromide ions in water
Colourless
What is the colour of Iodide ions in water
Colourless
describe the conversion of Fe2+ to Fe3+
all three halogen solutions are able to oxidise iron(II) ions into iron (III) ions.
in two seperate test tubes.
* add iron(II) sulfate and iron(III) chloride
* add sodium hydroxide (NAOH)
* Iron (II)sulfate + NaOH = Fe(OH)2 -> green percipate
* Iron (III) chloride + NaOH = Fe(OH)3 -> brown percipate
* Add chlorine water to Fe(OH)2
(when Cl2 is added to the Fe2+ mixture is oxdises the Fe2+ to Fe3+ (green - brown)
conculsion: chlorine oxdises the Fe2+ ions into Fe3+ ions
Describe the expeirment for oxidising sulfite ions
So3 2- –> So4 2-
* add sodium sulfite to test tube
* add chlorine
* (no change)
* add BaCl2
* (white ppt forms)
* add HCl
* (white ppt stays)
this proves the presence of sulfate ions
Describe the displacement of metals
Magnesium and Zinc are respectivily reacted with a solution of copper (II) sulfate
Colour of CuSO4 at beginning Blue
Colour at end colourless
colour of ppt formed Brown
other observations Gas evolved
In both casrs the metal (magnesium/zinc) displaces the copper from its salts
Blue to colourless
No CU2+ ions present
