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Chemistry > Oxidation and reduction > Flashcards

Oxidation and reduction Flashcards

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1
Q

list the three ways of looking at oxidation and reduction

A

addition or removal of oxygen
transfer of electrons
oxidation number

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2
Q

what are oxidtion reactions defined as

in terms of addition or removal of oxygen

A

Gaining oxygen

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3
Q

what are reduction reactions defined as

in terms of addition or removal of oxygen

A

loss of oxygen

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4
Q

what is reduction
In terms of oxygen

A

the removal of oxygen or the addition of hydrogen

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5
Q

Displacement reaction of metal oxides

in terms of addition or removal of oxygen

A

a more reactive metal will displace a less reactive metal from a compound

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6
Q

describe the thermite reaction

A

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

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7
Q

What is a displacement reaction of solutions

in terms of addition or removal of oxygen

A

A more reactive metal will displace a less reactive metal from a solution of one of its salts

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8
Q

Name an example of a displacement reaction

in terms of addition or removal of oxygen

A

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.

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9
Q

What is oxidation of an element

In terms of electron transfer

A

oxidation of an element takes place when it loses electrons

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10
Q

what is reduction of an element

In terms of electron transfer

A

reduction of an elemnet takes place when it gains electrons

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11
Q

Why do oxidation and reduction reactions occour together

In terms of electron transfer

A

When one reactant loses electrons the other has to gain electrons

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12
Q

Describe the Zinc and copper sulfate reaction

A

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.

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13
Q

What is a redox reaction

A

a reaction where oxidation and reduction occour simultaneously.( one cannout occour without the other)

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14
Q

an oxidation agent

A

substance that brings about oxidation in other substances

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15
Q

an reducing agent

A

substance that brings about reduction in other substances

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16
Q

What is oxidation number

A

the charge that an stoms has or appers to have when electrons are distrubuted according to certain rules

17
Q

what is electronegativity

A

the force of attraction that an atoms has for a shared pair of electrons

18
Q

What is oxidation

in terms of ON

A

increase in oxidation number

19
Q

what is reduction

in terms of ON

A

decrease in oxidation number

20
Q

oxidation number rules that have an expection

A

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

21
Q

What is transition metal

A

an element that forms at least one ion with a partially filled d sublevel

22
Q

Physical properties of transition elements

A

good conductors of heat and electricity
hammered or bend into shape easily
high melting points
hard + tough
high densities

23
Q

chemical properties of transition elements

A

less reactive than alkali metals
form coloured ions of different charges
some are very unreactive
many used as catlysts

24
Q

applications of oxidising agents

A

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)

25
Q

describe the reactions of the halogens

Reaction with hallides-compared to other halogens

A

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

26
Q

What is the colour of Chlorine in water

A

Pale green

27
Q

What is the colour of Bromine in water

A

Yellow/ orange

28
Q

What is the colour of Iodine in water

A

Brown/red

29
Q

What is the colour of Chloride ions in water

A

Colourless

30
Q

What is the colour of Bromide ions in water

A

Colourless

31
Q

What is the colour of Iodide ions in water

A

Colourless

32
Q

describe the conversion of Fe2+ to Fe3+

A

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

33
Q

Describe the expeirment for oxidising sulfite ions

A

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

34
Q

Describe the displacement of metals

A

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

Chemistry (21 decks)

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