Chapter 6 Oxidation and Reduction
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What is a redox reaction?
-A redox reaction is a chemical reaction involving the transfer of electrons between species. -One substance is oxidised (loses electrons) and another is reduced (gains electrons)
What happens to the oxidation number in oxidation and reduction?
In oxidation, the oxidation number increases. In reduction, the oxidation number decreases
How do you identify a redox reaction?
By looking for changes in oxidation numbers of species involved in the reaction
What is an oxidation half-equation and which side are the electrons on?
An equation that shows the species losing electrons. Electrons are on the right side.
What is a reduction half-equation and which side are the electrons on?
A equation that shows the species gaining electrons. Electrons are on the left side
How are redox equations balanced using half-equations?
-Write separate half equations -Equalise electrons -Add the equations -Cancel out species occurring on both sides
Why is an acidic medium often used in redox reactions involving polyatomic ions?
Because H+ ions are needed to balance the reaction, and acids like H2SO4 provide these ions without being oxidised or reduced
What are oxidation numbers of an atom?
It is the charge that atom would have if the compound was composed of ions
What does a positive oxidation number mean?
The atom loses electrons
What does a negative oxidation number mean?
The atom gains electrons
A oxidation number of 0 means..?
The atom neither gains nor loses electrons.
What does OIL RIG stand for?
Oxidation Is Loss Reduction Is Gain
When does a metal displacement reaction occur?
It occurs when a solid metal is added to an ionic metal solution
What is an oxidising agent?
A substance that causes oxidation by gaining electrons (it reduced itself)
What is a reducing agent?
A substance that causes reduction by losing electrons (it oxidises itself)
What is the oxidation number of an element in its standard state?
0
What is the oxidation number of hydrogen in most compounds?
+1, except in metal hydrides (MgH2) where it is -1
What is the oxidation number of oxygen in most compounds?
-2 except in peroxides like H2O2 where it is -1
How can you tell if a species has been reduced?
Its oxidation number decreases
What is a half-equation?
An equation showing either the oxidation or the reduction process separately, including electrons