3.1.7 Oxidation, Redox, Reduction Reactions Flashcards
Reducing agent
Lose electrons so they oxidise themselves
Oxidising agent
Gain electrons so they reduce themselves
Oxidation number of elements E.g. Cl2
0
Oxidation number of ions
Same as charge
Group 1 oxidation number
+1
Group 2 oxidation number
+2
Aluminium oxidation number
+3
Hydrogen oxidation number
+1
Except in hydrides it’s -1 E.g. NaH
What is a hydride
When hydrogen is bonded to a metal
Chlorine oxidation number
-1
Except in compounds with F and O E.g. ClF3 it’s Cl+3
Fluorine oxidation number
-1
Oxygen oxidation number
-2
Except in peroxides it’s -1
Except in OF2 it’s +2
When giving oxidation numbers what would H2O2 the oxidation state of oxygen be
-1
1) because peroxide
2) only given oxidation state of 1 oxygen not 2
How do you find oxidation state if molecule has a charge
The charges don’t add to 0 they add up to the charge on the molecule
Reduction is an increase/decrease in oxidation number
Decrease
Oxidation is an increase/decrease in oxidation number
Increase
Do you use big numbers in oxidation states
No
Steps on how to balance half equations
1) Write down what you have before and after
2) balance any atoms apart from oxygen and hydrogen
3) balance oxygens with water
4) balance hydrogens with H+ ions
5) balance charges with electrons
Example of 3 common peroxides
H2O2
BaO2
Na2O2
Do use use big numbers when finding charges when backing ionic equation
YES
What to do when combing half equations
Make electrons equal E.g. multiple one of the whole equation
Combine electrons should cancel
NO ELECTRONS IN FINAL EQUATION
