3.1.7 Oxidation, Reduction, and Redox Reactions Knowledge Flashcards
what is oxidation in terms of transfer of electrons?
the loss of electrons
what happens to the oxidation state, when a species is oxidised?
increases - number becomes more positive
what is reduction in terms of transfer of electrons?
the gain of electrons
what happens to the oxidation state, when a species is reduced?
decreases - number becomes more negative
what is a redox reaction?
reaction where oxidation and reduction take place at the same time
what is a reducing agent in terms of transfer of electrons?
- electron donor
- a reducing agent is itself oxidised
what is an oxidising agent in terms of transfer of electrons?
- electron acceptor
- an oxidising agent is itself reduced
what are oxidation states used for?
to follow the movement of electrons in redox reactions; to identify which substances have been oxidised and reduced
is the charge or number given first in oxidation states?
charge
what oxidation state do uncombined elements have?
0
what is the sum of all oxidation states in a compound?
0
what is the oxidation state of a simple ion equal to?
its charge
what is the sum of all oxidation states in a complex ion equal to?
its charge
what is the oxidation state(s) of hydrogen?
- usually +1
- in metal hydrides (e.g. LiH) -1
what is the oxidation state(s) of group 1 metals?
+1
what is the oxidation state(s) of group 2 metals?
+2
what is the oxidation state(s) of aluminium?
+3
what is the oxidation state(s) of oxygen?
- usually -2
- in peroxides (e.g. Na2O2), -1
- when reacted with fluorine (OF2), +2
what is the oxidation state(s) of fluorine?
-1
what is the oxidation state(s) of chlorine?
- usually -1
- is positive if reacted with oxygen or fluorine
what is the oxidation state(s) of bromine?
- usually -1
- is positive if reacted with oxygen or fluorine
what is the oxidation state(s) of iodine?
- usually -1
- is positive if reacted with oxygen or fluorine
why is the oxidation state of fluorine always -1?
it is the most electronegative element; no other element can remove an electron from fluorine
in what order are oxidation states assigned?
- Uncombined elements (0)
- Metals (G1, G2, Al)
- Fluorine (-1)
- Hydrogen (+1)
- Oxygen (-2)
- Chlorine (-1)
how do you balance a simple half-equation?
with e-
what are the rules for balancing complicated half-equations?
- balance the main atom (not H or O)
- Balance O using H2O
- Balance H using H+
- Balance charge using e-
what are the steps for combining half-equations?
- multiply one or both half-equations until they both contain the same no. electrons
- add the reactants from both half-equations together
- add the products from both half-equations together
- cancel out the electrons
what is a disproportionation reaction?
a reaction in which one type of atom is both oxidised and reduced
what is oxidation in terms of oxygen transfer?
gain of oxygen
what is reduction in terms of oxygen transfer?
loss of oxygen
what is an oxidising agent in terms of oxygen transfer?
substance which gives oxygen to another substance
what is an reducing agent in terms of oxygen transfer?
substance which removes oxygen from another substance.
what is oxidation in terms of hydrogen transfer?
loss of hydrogen
what is reduction in terms of hydrogen transfer?
gain of hydrogen
what is an oxidising agent in terms of hydrogen transfer?
oxidising agents remove hydrogen from another substance
what is an reducing agent in terms of hydrogen transfer?
reducing agents give hydrogen to another substance
