Electrochemistry Lecture Notes

This set of flashcards covers fundamental vocabulary, laws, and equations in electrochemistry, including cell types, electrode potentials, conductivity, and electrolysis as described in the lecture notes.

Electrochemistry

The study of relations between electrical energy and chemical energy in which a redox reaction takes place in a cell.

Electrolytic cell

A type of cell in which electrical energy is converted to chemical energy, commonly used for the extraction of aluminium and electroplating.

Electrochemical cell (Galvanic cell)

A type of cell in which chemical energy is converted to electrical energy, such as a Daniel cell, dry cell, or mercury cell.

Electrode potential

The potential difference (pd) between the electrode and the electrolyte.

Standard electrode potential

The electrode potential measured when the concentration of the solution is $1\,M$.

Reduction potential

The tendency of an electrode to accept electrons.

Reducing power

The tendency of an electrode to donate electrons or to reduce other substances.

Oxidation potential

The tendency of an electrode to donate electrons.

Oxidising power

The tendency of an electrode to oxidize other substances or to accept electrons.

Cell potential ($E_{cell}$)

The potential difference between the two electrodes of a cell, measured in volts ($V$).

Electromotive force (emf)

The potential difference between the reduction potential of the cathode and anode when no current is drawn through the cell.

Standard Hydrogen Electrode (SHE)

A reference electrode with a potential taken as zero ($0$), used to measure the electrode potential of a single electrode.

Nernst equation

An equation used to calculate the electrode potential at any concentration, given by $E_{M^{n+}/M} = E_{M^{n+}/M}^{\circ} - \frac{RT}{nF} \ln \frac{1}{[M^{n+}]}$.

Faraday constant ($F$)

The charge of one mole of electrons, valued at approximately $96500\,C$.

Gibbs free energy change ($\Delta_r G$)

The energy change in a cell expressed by the formula $\Delta_r G = -nFE_{cell}$.

Resistivity (Specific resistance)

The resistance of a conductor of one $cm^3$ or one $m^3$ volume ($\rho = R \times \frac{A}{l}$).

Conductance ($G$)

The reciprocal of resistance ($\frac{1}{R}$), measured in units of $ohm^{-1}$ or mho.

Conductivity (Specific conductance, $\kappa$)

The reciprocal of resistivity, defined as the conductance of a $1\,cm^3$ or $1\,m^3$ conductor.

Cell constant ($G^*$)

The ratio of the length ($l$) of a conductor to its area of cross-section ($A$).

Molar conductivity ($\Lambda_m$)

The conductance of a solution containing one mole of electrolyte kept between two electrodes at a unit distance apart with a large enough area of cross-section.

Kohlrausch's law

States that at infinite dilution, the limiting molar conductivity of an electrolyte is equal to the sum of the limiting molar conductivities of all its ions.

Faraday's 1st Law of Electrolysis

States that the mass of a substance deposited or liberated during electrolysis is directly proportional to the quantity of electricity passed through it ($m = Z \times I \times t$).

Electrochemical equivalent ($Z$)

The mass of a substance deposited when a current of $1\,A$ is passed for $1\,s$.

Faraday's 2nd Law of Electrolysis

States that when the same quantity of electricity is passed through different electrolytes in series, the mass of substances deposited is directly proportional to their chemical equivalent masses.

Primary cells

Cells in which the chemical reaction occurs only once and the battery becomes dead after a period of time, such as a dry cell (Leclanch cell).

Secondary cells

Cells that can be reused or recharged by passing a current through them in the opposite direction, such as a lead storage battery or $Ni-Cd$ cell.

Fuel cell

A cell designed to convert energy produced from the combustion of fuels like hydrogen and oxygen directly into electrical energy.

Corrosion

The process of the "eating away" of a metal due to the presence of $O_2$, moisture, and atmospheric gases to form oxides, carbonates, or sulfides.

Rusting

The specific corrosion of iron ($Fe$) resulting in hydrated ferric oxide ($Fe_2O_3 \cdot xH_2O$).

Active anodes

Electrodes that take part in the chemical reaction during electrolysis, such as $Cu$, $Ag$, or $Ni$.

Inert anodes

Electrodes that do not take part in the chemical reaction during electrolysis, such as platinum ($Pt$) or graphite.