BELLWORK Balance the following redox reaction using the “half-reaction” method HNO 2 + I - NO + I 2 2e - + 2H + + 2 HNO 2 2 NO + 2H 2 O 2 I - I 2 + 2e - 2H + + 2HNO 2 + 2I - 2NO + 2H 2 O + I 2
Electrochemical cells produce an electric current from redox reactions CAN ALSO BE CALLED A Voltaic cell Galvanic cell Battery
A simple battery separates the reduction reaction from the oxidation reaction so that the electrons must travel through a wire
Oxidation e - e - e - e - e - e - e - Reduction
Lose e - e - e - e - e - e - e - e - e - e - e - e - Gain e -
When a wire connects the half cells an electrical current is created. This can’t occur for long because positive charge will build up at the anode and negative charge will build up at the cathode A salt bridge is used to keep the two cell compartments neutral
The salt bridge contains a salt (positive and negative ions) that flows into each beaker as needed to keep the charge neutral
The salt bridge completes the circuit and the current will continue to flow
SALT BRIDGE Gotta have it!!!
How do you determine the voltage of a battery?
Use the table of reduction potentials .
All of the half-reactions are for reduction
E º is the electrical potential of the ½ reaction in Volts
If you need the oxidation potential, flip the equation and change the sign of E º. All reduction potentials are reversible.
The top of the table = elements that are easily reduced, and not easily oxidized. They take electrons easily.
The bottom of the table= elements that are easily oxidized and not easily reduced. They give electrons easily.
To determine the voltage of a battery you add the voltages of the two half-reactions