Chapter 23: Redox & Electrode Potentials Flashcards
Define Reduction and oxidation
- Reduction: gain of electrons/ gain of hydrogen/ decrease in oxidation number.
- Oxidation: Loss of electrons/ loss of hydrogen/ increase in oxidation number.
Oxidation and reducing agents
Oxidising agent: oxidises another species by reducing itself.
Reducing agent: Reduces another species by oxidising itself.
What is a voltaic cell?
A type of electrochemical cell that converts chemical energy into electrical energy.
What is a half cell?
Contains one chemical species of a redox reaction.
2 are needed for a voltaic cell. They must be separated or they will flow in an uncontrolled way and generate heat energy rather than electrical energy.
Metal/metal ion half-cells
Electrode made of solid metal. The solution is made of 1 moldm-3 of the corresponding metal ions.
The two half cells are connected by a salt bridge which completes the circuit and allows current to flow.
A voltmeter is also attached
Ion/ion half cells
- Electrode is platinum because it is inert.
- each electrolyte contains 1 moldm-3 of the ion solutions.
Standard electrode
A half cell contain H2 gas, 1 moldm-3H+ ions in the electrolyte and a platinum electrode.
They also have standard conditions such as 298k 10.kPa and 1moldm-3
All other electrode potentials are compared to this one
Standard electrode potentials is 0V
Definition of standard electrode potential
The e.m.f of a half cell connected to a standard hydrogen half-cell under standard conditions of 298k, 1moldm-3 and 100kpa
A more negative or positive Standard electrode potential means (E theta)…
More negative:
The species is more likely to undergo oxidation. The greater the reactivity of a metal.
More positive:
The species is less likely to undergo oxidation. The greater reactivity of a non-metal.
Equation for standard cell potential
Standard cell potential= Electrode potential of positive electrode- Electrode potential of negative electrode
