redox I Flashcards

1
Q

what is the oxidation number of uncombined elements/diatomic molecules?

A

0

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2
Q

what is an oxidation number?

A

the number of electrons an atom has donated/accepted to form an ion

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3
Q

what is the oxidation number of a monatomic ion?

A

its charge e.g. Na+ has an oxidation number of +1

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4
Q

what is an oxidising agent?

A

accept electrons and become reduced

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5
Q

what is a reducing agent?

A

they donate electrons and become oxidised

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6
Q

what is oxidation?

A

loss of electrons, molecule becomes positive

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7
Q

what is reduction?

A

gain of electrons, molecule becomes negative

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8
Q

what is a disproportionation reaction?

A

when an element in a single species is simultaneously oxidised and reduced

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9
Q

what is the oxidation state of hydrogen?

A

+1 EXCEPT in metal hydrides where its -1

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10
Q

what is the oxidation state of oxygen?

A

-2 EXCEPT in peroxides where it is -1

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11
Q

what is the oxidation state of aluminium?

A

always +3

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12
Q

what is the oxidation state of fluorine?

A

always -1

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13
Q

what is the oxidation state of chlorine?

A

-1 EXCEPT if in a compound with oxygen or fluorine where it would be positive

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14
Q

what happens to the oxidation number if electrons are lost?

A

increases by 1 for every lost electron

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15
Q

what happens to the oxidation number if electrons are gained?

A

decreases by 1 for every gained electron

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16
Q

what usually happens when a non-metal forms a compound?

A

forms negative ions by gain of electrons
with a decrease in oxidation number

17
Q

what usually happens when a metal forms a compound?

A

forms positive ions by loss of electrons with
an increase in oxidation number

18
Q

why are oxidation numbers useful?

A

can classify reactions as redox and as disproportionation

19
Q

what should be balanced first in a half equation?

A

anything that isn’t water or oxygen gas