3: Redox I Flashcards
What are the definitions of oxidation
- Addition of oxygen
- Loss of hydrogen
- Loss of electrons
What are the definitions of reduction
- Loss of oxygen
- Addition of hydrogen
- Gain of electrons
What is OILRIG
Oxidation is loss of electrons, reduction is gain of electrons
What is oxidation number
The charge that would exist on an individual atom if the bonding were completely ionic
What is the oxidation number of uncombined elements
0
What is the oxidation number of a cation
+ (charge)
What is the oxidation number of an anion
- (charge)
What do roman numerals indicate
The oxidation state of ions in a compound
What is the oxidation state of a mono-atomic atom (e.g. Zn+2)
The same as the charge on the ion (e.g. +2)
What is the sum of the oxidation numbers in a compound (e.g. NaCl)
0
What is the sum of oxidation in an ion (e.g. SO4-2)
Equal to the charge (e.g. -2)
What is given the oxidation number in compounds or ions
The more electronegative element is given the negative value
What is the oxidation state of group 1 elements
Always +1
What is the oxidation state of group 2 elements
Always +2
What is the oxidation state of fluorine
Always -1
What is the oxidation state of hydrogen
+1 (except in metal hydrides where it’s -1)
What is the oxidation state of oxygen
-2 (except in peroxides where it’s -1, and F2O where it’s +2)
What is the oxidation number in molecules or compounds
The sum of the oxidation numbers is 0
How do you determine the element with a positive oxidation state in a molecule/compound
The more electronegative value has the negative value
How to determine the oxidation number
- Group in periodic table
- Other elements in formula
- Following oxidation rules
- Certain species can have varying oxidation states!
How can oxidation and reduction in terms of electron transfer be demonstrated
What is an oxidising agent
A substance that oxidises another atom/ion by causing it to lose electrons, whilst itself gaining electrons and being reduced. Its oxidation number becomes more negative
What is a reducing agent
A substance that reduces another atom/ion by causing it to gain electrons, whilst itself losing electors and being oxidised. It’s oxidation number becomes more positive
What is a redox reaction
Oxidation and reduction must occur, there is both a reducing and oxidising agent present
How to determine the strongest oxidising/reducing agent
The species which oxidation number changes the most dramatically
What is a disproportionation reaction
A reaction in which the same species is simultaneously oxidised and reduced
How to balance disproportion reactions
- Deduce oxidation number changes
- Balance oxidation number changes
- Balance charges
What are the usual oxidation states of metals
- Positive values in compounds
- Value usually that of the group number
- With several oxidation number possibilities the value is no higher than the group number
- Generally oxidised
What are the usual oxidation numbers of non-metals
- Mostly negative based on usual ions
- Can have values up to their group number
- Generally reduced
How to write and balance full ionic equations
