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AQA A Level Physical Chemistry > 7. Oxidation, Reduction & Redox > Flashcards

7. Oxidation, Reduction & Redox Flashcards

1
Q

What is oxidation?

A

Loss of electrons, gain of oxygen

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2
Q

What is reduction?

A

Gain of electrons, loss of oxygen

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3
Q

What is a redox reaction?

A

In any reaction where an element is oxidised, and another must be reduced

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4
Q

What happens if an element itself is oxidised?

A

It must reduce the other element (by donating electrons)

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5
Q

What is the element that is oxidised known as?

A

The reducing agent (reductant)

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6
Q

Why is the element that is oxidised known as the reducing agent?

A

It must reduce the element by donating electrons

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7
Q

What happens if an element itself is reduced?

A

It must oxidise the other element (by accepting electrons)

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8
Q

What is the element that is reduced known as?

A

The oxidising agent (oxidant)

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9
Q

Why is the element that is reduced known as the oxidising agent?

A

It must oxidise the element by accepting electrons

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10
Q

What is used when it is unclear which element has been oxidised and which reduced?

A

Oxidation number/state of an element

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11
Q

Are S block metals oxidising or reducing agents?

A

Reducing - they lose electrons in reactions and so are oxidised

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12
Q

Do s block metals have positive or negative oxidation numbers?

A

Positive

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13
Q

Which elements will need to have their oxidation numbers worked out?

A

P and d block elements

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14
Q

Why do p and d block elements have to have their oxidation numbers worked out?

A

They can exhibit more than one oxidation state when they form compounds

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15
Q

Are halogens oxidising or reducing agents?

A

Oxidising - they gain electrons and so are reduced

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16
Q

Which element in a compound is taken as the one with a negative oxidation state?

A

The most electronegative element

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17
Q

Why is the most electronegative element the one with a negative oxidation state?

A

It has more power to withdraw electron density

18
Q

Oxidation state of an uncombined element?

A

Zero

19
Q

Oxidation state of a simple ion? Are there any exceptions to this?

A

Charge on ion - exception in some cases (e.g. halogens, hydrogen, oxygen)

20
Q

Oxidation state of group 1 elements in a compound? Are there any exceptions to this?

A

+1 - no exceptions

21
Q

Oxidation state of group 2 elements in a compound? Are there any exceptions to this?

A

+2 - no exceptions

22
Q

Oxidation state of fluorine? Are there any exceptions to this?

A

-1 - no exceptions

23
Q

Oxidation state of oxygen? Are there any exceptions to this?

A

-2 - except when in peroxides and combined with F

24
Q

Oxidation state of hydrogen? Are there any exceptions to this?

A

+1 - except in metal hydrides

25
Q

Oxidation state of chlorine? Are there any exceptions to this?

A

-1 - except when with O or F

26
Q

What is the sum of oxidation states of all elements in a compound?

A

Zero

27
Q

What is the sum of the oxidation states of elements in a polyatomic ion equal to?

A

The charge on the ion

28
Q

Why is oxygen’s oxidation number not -2 when combined with F?

A

F is more electronegative

29
Q

What is the oxidation number of S in H₂SO₄?

A

+6

30
Q

What can oxidation states be used to determine?

A

What has been oxidised and reduced in a reaction (therefore oxidising and reducing agents)

31
Q

What does it mean if the oxidation state of an element increases?

A

It has been oxidised

32
Q

What does it mean if the oxidation state of an element decreases?

A

It has been reduced

33
Q

When is a reaction not redox?

A

When there is no change in oxidation state in a reaction

34
Q

What is a disproportionation reaction?

A

A redox reaction in which the same substance is both oxidised and reduced

35
Q

Which substances can be split into ions for half equations?

A

Ionic substances only

36
Q

What happens to polyatomic ions in half equations?

A

They are not split up into individual element

37
Q

What balances oxygen in half equations?

A

Water

38
Q

What balances excess hydrogen from water in half equations?

A

H+ ions

39
Q

In overall redox equations, what needs to be cancelled out?

A

Electrons

40
Q

How are overall redox equations formed?

A

By adding the two half equations together - after ensuring the number of electrons are equal (and therefore cancel)

AQA A Level Physical Chemistry (12 decks)

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