Redox
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What is a redox reaction?
A reaction that involves both reduction and oxidation
Give an example of a half equation for oxidation and reduction
Oxidation Mg —> Mg2+ + 2e- Reduction O2 + 2e- —> O2-
What does OILRIG stand for?
Oxidation Is Loss Reduction is Gain (of electrons)
What happens to the oxidation number in an oxidation reaction?
It increases
What happens to the oxidation number in a reduction reaction?
It decreases
Give the oxidation state of an uncombined element
0
Give the oxidation states of metals combined in a compound (Group 1 to 3)
Group 1 = +1 Group 2 = +2 Group 3 = +3
Give the oxidation number of fluorine when combined in a compound
-1
Give the oxidation number of hydrogen when combined in a compound. Are there any exception?
+1. In metal hydrides it is -1
Give the oxidation number of oxygen when combined in a compound. Are there any exceptions?
-2. In peroxides, combined with fluorine, F will be -1 and O will be positive
Give the oxidation number of chlorine
-1
When is a roman numeral used to indicate the oxidation number of an element?
In transition metals or oxyanions (negative ions that contain oxygen ‘ate). These are elements that can exist with more than one oxidation state
Why Ag and Zn not require roman numerals indicating their oxidation state?
They are not transition metals as Ag always forms +1 ions and Zn always forms 2+ ions
Give the definition of an oxidising agent
Gains electrons/ is reduces (oxidises another species)
Give the definition of a reducing agent
Loses electrons/ is oxidised (reduces another species)
What does MASH stand for?
Metals + acids —> salt + hydrogen
Do metals tend to undergo oxidation or reduction? Explain why
• Oxidation - they lose electrons forming positive ions. Their oxidation number increases
Do non-metals tend to undergo reduction or oxidation? Explain why
• Reduction - they gain electrons forming negative ions. Their oxidation number decreases