3.1 Physical Chemistry: .7 Oxidation, reduction and redox reactions Flashcards
what is oxidation?
the loss of electrons
what is reduction?
the gain of electrons
what is an oxidising agent?
atom/molecule that accepts electrons and gets reduced its self
what is an reducing agent?
atom/molecule that donates electrons and gets oxidised its self
what does the oxidation state of an element tell you?
-it tells you the total number of electrons it has donated or accepted
what are the oxidation states of elements?
0
what are the oxidation states of elements bonded to identical atoms?
0
what are the oxidation state of an overall compound?
the ion charge
e.g if has no charge the oxidation is 0
if it has a charge of -2 then the oxidation state is -2
what is the oxidation state of a simple monatomic ion?
it is the same as its charge
e.g Na+ would have oxidation state of +1
what is the oxidation state of elements in group 1 in a compound?
+1
what is the oxidation state of elements in group 2 in a compound?
+2
what is the oxidation state of elements in group 6 in a compound?
-2
what is the oxidation state of elements in group in group 7?
-1
what is the oxidation state of oxygen,
what are the exceptions?
- the oxidation state of oxygen is -2
- but when oxygen is in a peroxide it is -1 H2O2
- when it is bonded with fluorine it is +2 e.g OF2
- when its in O2F2 it is +1
what is the oxidation state of chlorine? what are the exceptions?
- the oxidation state of Chlorine is -1
- BUT when it is bonded with Oxygen it is +1
what is the oxidation state of Hydrogen? what are the exceptions?
- the oxidation state of Hydrogen is +1
- BUT when it is bonded with any element in group 1 it is -1
what is the oxidation state of Cl in the Chlorate (I) ion (ClO-)
+1
because…
Cl O-
+1 -2= -1
what does an increase in oxidation number mean?
- it means that the chemical has gone through oxidation
- there has been a loss of electrons
what does a decrease in oxidation number mean?
- it means that the chemical has gone through reduction
- there has been a gain of electrons
state whether this reaction is a redox reaction?
Zn + 2HCl –> ZnCl2 + H2
Zn + 2HCl –> ZnCl2 + H2
ox no of Zn= 0
ox no of H=+1
ox no of Cl= -1
ox no of Zn= +2
ox no of Cl= -1
ox no of H= O
Zn has gone up in oxidation number so it is oxidation
Hydrogen has gone down in oxidation number so it reduction.
Therefore this is a redox reaction.
in this reaction state which is the oxidant and which is the reducing agent
Zn + 2HCl –> ZnCl2 + H2
H+ is the oxidant (it oxidised the Zn)
Zn is the reducing agent (it reduces the H+ ion)
when balancing a combined ionic equation, what are the steps that you should follow?
- work out the oxidation states of each element
- work out the electrons
- work out if there water molecules and H+ ions are required
- balance the electrons
