CHEM 30: Electrochemistry

Oxidize

When a substance LOSES its electrons.

Reduced

When a substance GAINS its electrons.

Redox Reaction

The net reaction of oxidation and reduction.

Oxidation and Reduction

Occur together in ONE reaction.

Oxidizing Agent

A substance that gets reduced causes another substance to be oxidized.

Reducing Agent

A substance that gets oxidized cause another substance to be reduced.

Disproportionation

A reaction in which the same substance functions as both the oxidizing agent and a reducing agent; it is both reduced and oxidized.

Oxidation Number

A positive or negative number that allows you to determine what is happening to the electron in the reaction.

Oxidation Number Increaese

The substance is being OXIDIZED.

Oxidation Number Decrease

The substance is being REDUCED.

Oxidization States Constants

All atoms: 0

Hydrogen: +1, except in hydrides then -1

Oxygen: -2, except in peroxides then -1

Monatomic inons: charge on ion

Spontaneity Rule

If the OA is above the RA pn the redox half reaction table.

5 Step Methode

Step 1: list all entities present and classify as OA and RA and SOA and SRA.

Step 2: Write down the half reactions for the SOA.

Step 3: Write down the half reactions for the SRA.

Step 4: Balance the electrons in both half reactions and put the two half reactions together.

Step 5: Perdict spontinaity.

Voltaic Cell

An electrochemical cell that spontaneously reacts to PRODUCE electricity.

Electrolytic Cell

An electrochemical cell that USES electricity to cause a non-spontanious chemical change.

Electrode

The solid in the half-cell where the wires attach.

Anode

The electrode where oxidization occurs, where the strongest RA reacts.

Cathode

The eletrode where reduction occurs, where the strongest OA reacts.

Anion

A negative ion, moves toward the anode.

Cation

A postive ion, moves toward the cathode.

Salt Bridge

A barrier the keeps the solutions in a voltaic cell apart, but allows the flow of ions between the solutions to prevent an electrical charge build up. Required by Voltaic Cells

Electrolyte

A substance the conducts electricity when dissolved in water.

Power Supply

An electronic device that replaces a battery.

External Circuit

The wires that are used to connect the anode to the cathode.

Electron Flow

Anode to Cathode.

Ion FLow

Anions to Anode; Cations to Cathade.

Cell Spontanaity

Voltaic: yes

Electrolytic: no

Net Electrode Potencial of Cells (E°net )

Voltaic: positve

Electrolytic: negative

Line Notion of Cells

anode / anode electrolyte // cathode electrolyte / cathode

Chloride Anomaly

When chloride acts as the reducing agent when with water in a reaction.

Standard Hydrogen Half-Cell

What is used to measure the standard reduction potentials. It contains 1.00 mol/L of the hydrogen ion.

Standard Cell Difference Equation

E°net= E°r(cathode) - E°r(anode)

Calculating Cell Potential Difference

Step 1: List all entities present

Step 2: Determine OAs and RAs

Step 3: Determine SOAs and SRAs

Step 4: Write down anode and cathode half reactions (redox half reactions)

Step 5: Calculate the cell potential difference

Spontaneity in Electrochemical Cells

If OA is above the RA, it is spontaneous.

If the cell potential is positive, the reactions is spontaneous.

Faraday's Constant

9.65 x 10^4 C/mol → it represents the number of coulombs per mole of electrons.

Moles of an Electron Equation

(I x t)/F

I = amps

t = time in seconds

F = Faraday's constant in C/s