Oxidation & Reduction Flashcards
what is a redox reaction
is a process in which electrons are transferred from one species to another
what is a reducing agent
the species that donates the electrons, this is said to be oxidised
what is the oxidising agent
the species that gains the electrons is said to be reduced, and is called an oxidising agent because it cause the oxidation of another species.
mnemonic for remembering oxidising agent and reducing agent
OILRIG
Oxidation
Is
Loss
Reduction
Is
Gain
important thing to note about oxidation and reduction
they always occur together. one cannot occur without the other, cause there needs to be a flow of electrons from the species that is oxidised to the one that is reduced.
how to tell if its reduction
if electrons are includes in reactants, its reduction
h0ow can the process of oxidation and reduction be shown through
half-equations, which can be combined to show full redox reaction. they can also be used to determine whether species is being oxidised or reduced.
important key point to note about redox reactions
some agents only function in redox reaction when the solution is acidic, which requires the presence of hydrogen ions in solution.
how to combine two half-equations to produce full equation for reaction occuring
number of electrons in both half-equations must be same, meaning number of electrons produced from oxidation of a species are consumed in the reduction of another.
how to tell if its oxidation
if electrons are in the products its oxidation.
how to balance half equations when given the species being oxidised/reduced.
1) add water to balance the amount of oxygen on both sides, and then make up for any unbalanced hydrogens buy adding hydrogen ions
2) balance the charge on both siddes by adding electrons
how can combine two half-equations to produce full equation for reaction occurring be achieved
by multip;ying one or both half-equations bu an interger value to balance the number of electrons. once combined, electrons should cancel out, so no electrons are shown in the full equation.
4 common chemical reactions operating via an electron-transfer
- metal-metal ion displacement
- halogen-halide displacement
- combustion
- corrosion
explain metal-metal ion displacement
electrons are transferred from halide ions form a metal element the metal element is hence oxidised to form metal ions, and the metal ions are reduced to a metal precipitate
explain halogen-halide displacement
electrons are transferred from halidei pns to a halogen. the halide ions are oxidised to form the elemental halogen, while the halogen is reduced to halide ions.
explain the chemical process of combustion
a fuel is oxidised in the presence of oxygen gas, which is reduced.
explain the chemical process of corrosion
a metal (usually iron) is oxidised, while oxygen is reduced.
what is an oxide
as oxygen is reduced it forms a compound with the metal ions called an oxide
why do some metals have a natural resistance to metal
they form a protective oxide coating on the surface of the metal when exposed to air, which prevents further oxidation
what are other methods to prevent corrosion of more reactive metals
plating then with more reactive metals (metals that are more likely to be reduced), a sacrificial anode, or cathodic protection.
what are oxidation numbers
numerical values assigned to atoms (whether atom exists by itself, or in a molecule or compound).
the oxidation number of atom can be thought of as the hypothetical charge on the atom if it were ionically bonded.
what do oxidation numbers do
allow us to keep track of electron exchange and allow us to determine whether or not redox reaction is taking place.
if oxidation number of species increase (gets more positive)
over the course of a reactio, the species is oxidised
if the oxidation number decreases (gets more negative)
the species is reduced.
