Redox processes Flashcards
The oxidation state of all elements is
zero
The sum of the oxidation states in a molecule/ion =
the charge of the molecule/ion
Oxygen in a compound has an oxidation state of
-2
Hydrogen in a compound has an oxidation state of ___ *Except if it is bonded to a metal, when the charge is ___
+1, -1
Fluorine in a compound has an oxidation state of
-1
Oxidation state of metals in a compound =
+(valence electrons)
Halogens are probably __, but can be flexible
-1
adding oxygen is (oxidation/reduction)
oxidation
removing oxygen is (oxidation/reduction)
reduction
Removing hydrogen is (oxidation/reduction)
oxidation
Adding hydrogen is (oxidation/reduction)
reduction
Loss of electrons is (oxidation/reduction)
oxidation
Gain of electrons is (oxidation/reduction)
reduction
Increase in oxidation state is (oxidation/reduction)
oxidation
Decrease in oxidation state is (oxidation/reduction)
reduction
an oxidising agent is
itself reduced
Deduce redox equations using half equations:
Split into obvious half equations Balance electrons (they should be on opposite sides of the two equations)
Balancing half equations in acidic solution:
Split into two half equations Balance anything obvious add : H2O H+ E- Multiply half equations so that the number of electrons are equal Combine and cancel
In a redox equation, the most reactive element ends up as
an ion
In a voltaic cell, The negative electrode (the one higher up the reactivity series) ___ and the positive electrode ____
oxidises, reduces
Difference between an electrolytic cell and a voltaic cell
Electrolytic cell - uses electricity to convert electrical energy to chemical energy
Voltaic cell - makes electricity, chemical energy to electrical energy
What are salt bridges usually made out of and why?
NaNO3 because it’s very unreactive
What is the purpose of the salt bridge?
Completes the circuit
Balances the charge in the half cells
in a voltaic cell, which is the anode and which is the cathode?
anode - negative
cathode - positive
in an electrolytic cell, which is the anode and which is the cathode?
anode - positive
cathode - negative
What is the purpose of wires in an electrolytic cell?
Wires conduct the electricity and are unchanged
What is an electrolyte -
a substance that conducts electricity as a liquid and is chemically decomposed in the process. As a solid, it is an insulator
What are electrodes usually made of in electrolytic cells?
graphite or platinum, both of which are unreactive
Which direction do the electrons move?
Towards the cathode
What are the charge carriers in an electrolytic cell?
In the wires, electrons
In the electrolytes, ions
