Can someone please explain to me how to identify and assign oxidation states in
ID: 793168 • Letter: C
Question
Can someone please explain to me how to identify and assign oxidation states in a redox reaction?
I am really confused, I have been reading the chapter and I get how to tell when something loses or gains electrons (what is being reduced or gain in the equation).
But I am completly lost on where to get these oxidation states from???
For example: Cd(s) + NiNO2(s) + H2O (l) --> Cd(OH)2(s) + Ni(OH)2(s)
Oxidation state:0..........+4,-2............+1,-2...........+2,-2,+1.........+2,-2,+1
That is the oxidation states for that equation, but I have no clue how to get them.
Please explain!
Explanation / Answer
Electrochemical reactions involve the transfer of electrons. Mass and charge are conserved when balancing these reactions, but you need to know which atoms are oxidized and which atoms are reduced during the reaction. Oxidation numbers are used to keep track of how many electrons are lost or gained by each atom. These oxidation numbers are assigned using the following rules:
For example, in NaH, the H is H-; in HCl, the H is H+.
The atoms in He and N2, for example, have oxidation numbers of 0.
For example, the oxidation number of Na+ is +1; the oxidation number of N3- is -3.
The oxidation number of hydrogen is -1 in compounds containing elements that are lesselectronegative than hydrogen, as in CaH2.
Exceptions include OF2, since F is more electronegative than O, and BaO2, due to the structure of the peroxide ion, which is [O-O]2-.
The oxidation number of Cl is -1 in HCl, but the oxidation number of Cl is +1 in HOCl.
For example, the sum of the oxidation numbers for SO42- is -2.