CHMY172 Chapter 17: Electrochemistry and Redox Reactions

Balancing redox reactions step 1

Identify what is being reduced, and what is being oxidized

Balancing redox reactions step 2

Balance everything that is NOT H or O

Balancing redox reactions step 3

Balance O by adding H₂O

Balancing redox reactions step 4

Balance H by adding H⁺ ions

Balancing redox reactions step 5

Balance e^- for each half reaction

Balancing redox reactions step 6

Balance e^- between half reactions

Balancing redox reactions step 7

Combine half reactions

Balancing redox reactions step 8

If in a basic environment, add in OH^- to cancel H⁺

Electrochemistry

How electrons move in reactions

Redox reactions

Oxidation-reduction reaction, one gains e^-, one loses e^-

Reduction

Gaining e^-

Oxidation

Losing e^-

OIL RIG

Oxidation is loss, reduction is gain

What steps in balancing redox reactions are not always required?

Steps 2 and 8

Salt bridge

Generate ions for regeneration of cations and anions

Cell notation

anode (s) | M anion (aq) || M cation (aq) | cathode (s)

+ charge

e- was lost

- charge

e- was gained

Cathode

Where reduction is occurring

Anode

Where oxidation is occurring

Galvanic cell

Redox reactions occur separately via a conductive wire and salt bridge

How can redox reactions occur when they are apart?

Using a wire for conductivity

E^o

Electric potential

Spontaneous

Have a positive electric potential value, the reaction is likely to occur naturally

Non-spontaneous

Have a negative electric potential value, the reaction is not likely to happen on its own

Concentration cell

The voltage between two cells with the same salt and metal but different concentrations will reach 0