Redox (HL)

the passing of electrical energy from a power supply, such as a battery, through a conducting liquid

The current is created because the electrons are pushed into the negative terminal by the battery and pulled out of the positive terminal. It is the migration of ions within the liquid (electrolyte) which is molten in this case that completes the circuit as they flow to the oppositely charged terminals there are no half cells in an electrolytic cell, everything occurs in one beaker

Electromotive force: the electrical pressure that causes electrons to flow through the conduc- tor. It is termed the cell potential (E not value; maximum amount of energy that can be generated from the passing of electrons

Ecell = Ecathode - Eanode

the half-cell consisting of an inert platinum electrode immersed in 1 M HCl (acidic solution) with hydrogen gas at 1 atm/ 100kPa bubbling through the solution; used as the standard cell potential of zero it has a standard electrode potential of 0 V and half equation that occurs is 2H+ + 2e- -> H2 hydrogen ion is the oxidizing agent (reduced) and hydrogen gas (oxidized) the reducing agent The electrochemical series and the standard electrode potentials have been measured by connecting the half cells containing solutions of 1 moldm-3 or 100kPa for gases to the SHE and measuring the strengths of the oxidant and reductant

The voltage measured under standard conditions when a half cell is connected to a standard hydrogen electrode. This connections is by the means of an external circuit as well as salt bridge. To maintain standard conditions, the conc of all aqueous solutions must be 1.0 moldm-3, temperature 298 K and pressure 100kPa

water can be oxidized to oxygen at the anode and reduced to hydrogen at the cathode the reaction that will occur at the cathode is the species that is the strongest oxidant / oxidizing agent present (most readily reduces) in other words species that can is the lowest in the electrochemical series (because highest is the reducing agent or more readily oxidized species)

lowest reduction potential value and favored to oxidize (best reducing agent)

E = Ecat - Ean E = reduction - oxidation E for oxidation (-) E for reduction (+) If E is negative this means Ecat < Ean and it is non spontaneous (Gibbs free energy is negative) If E is positive this means Ecat < Ean and it is non spontaneous (Gibbs free energy is negative)

ΔG = -nFE n; number of moles F; faradays constant E; Ecat-Ean G; Gibbs free energy if Gibbs free is negative, spontaneous if Gibbs free is posisitve, non spontaneous if E is negative, non spontaneous (electrolytic) if E is positive, spontaneous (voltaic)

Determines the relative amounts of products formed during electrolysis where Q: is the charge in coulombs I: is the current in amps t: time in seconds

-time the current is passed through -electric current -charge of the ion (single charged ion will produce way more than something that has a 2+ or 3+ charge)

E = Ecat - Ean E = reduction - oxidation E for oxidation (-) E for reduction (+) If E is positive it will be a spontaneous reaction (voltaic)

The charge of one mole of electrons is 96 500 C. The charge of one mole of electrons is known as Faraday's law and given the symbol F 1 Faraday = 96 500 Cmol-1 Therefore, Q = n(e-)F section 2 in Data Booklet