Oxidation and reduction Flashcards

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
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
26
What is the colour of Chlorine in water
Pale green
27
What is the colour of Bromine in water
Yellow/ orange
28
What is the colour of Iodine in water
Brown/red
29
What is the colour of Chloride ions in water
Colourless
30
What is the colour of Bromide ions in water
Colourless
31
What is the colour of Iodide ions in water
Colourless
32
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
33
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
34
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