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# (Urgent) Oxidation numbers and redox. watch

1. In the ocr book there is an example of "redox in terms of oxidation numbers" (page 51) and the chemical equation is Cu + 2AgNO3 -> 2Ag + Cu(NO3)2.

So Cu has an oxidation number of 0 because all elements have an Ox Num of 0.
In the book it says 2Ag has an oxidation Num of +1 in 2AgNO3 but an oxidation number of 0 for 2Ag in the products of the reaction. Also Cu becomes +2 for Cu(NO3)2.

Can someone please explain how a redox reaction occurs with oxidation numbers and how to know the oxidation number of a compound like 2Ag.

Thank you.
In the ocr book there is an example of "redox in terms of oxidation numbers" (page 51) and the chemical equation is Cu + 2AgNO3 -> 2Ag + Cu(NO3)2.

So Cu has an oxidation number of 0 because all elements have an Ox Num of 0.
In the book it says 2Ag has an oxidation Num of +1 in 2AgNO3 but an oxidation number of 0 for 2Ag in the products of the reaction. Also Cu becomes +2 for Cu(NO3)2.

Can someone please explain how a redox reaction occurs with oxidation numbers and how to know the oxidation number of a compound like 2Ag.

Thank you.
Redox is all about gain and loss of electrons:

O xidation
I s
L oss
R eduction
I s
G ain

OILRIG

The silver changes from an oxidation state of +1 to 0
Hence it has gained one negative charge, therefore it has been reduced.
The copper changes from 0 to +2, therefore it has lost two electrons. It has been oxidised.
3. (Original post by charco)
Redox is all about gain and loss of electrons:

O xidation
I s
L oss
R eduction
I s
G ain

OILRIG

The silver changes from an oxidation state of +1 to 0
Hence it has gained one negative charge, therefore it has been reduced.
The copper changes from 0 to +2, therefore it has lost two electrons. It has been oxidised.

Thanks that makes sense. But how would you know that silver has an oxidation number of +1 in the beginning?
Thanks that makes sense. But how would you know that silver has an oxidation number of +1 in the beginning?
Rules of oxidation numbers:

1. The sum of all oxidation numbers in a species equals the charge on the species (hence elements are always zero).
2. For simple ions, the oxidation number is the same as the ionic charge.
3. In any species the most electronegative atom takes a negative oxidation state
4. Hydrogen is always +1 (except when rule 3 applies)
5. Oxygen is always -2, except for peroxides (-1) and rules 1 & 3.

AgNO3 is ionic therefore Ag+ has an oxidation number of +1 (rule 2)

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