redox ii

Which blocks of periodic table undergo oxidation / reduction

Oxidation- s block, d block and p block

Reduction - p block

Standard electrode potential

The voltage or electromotive force of a half cell when it is connected to a standard hydrogen electrode under standard conditions

How do electrochemical cells work

Use redox reactions since the electron transfer between products creates a flow of electrons ( a current)

Standard hydrogen electrode and standard conditions

Used as a reference for all half cell potentials as it has a standard electrode potential of zero

Standard conditions:

-solutions of 1.0mol dm-3 conc

-298K

-100kPa pressure

Electrochemical cell set up

2 components called half cells, the potential difference is cell potentials

Salt bridge

Needed to complete the electrical circuit, usually made of a conc solution of potassium nitrate solution soaked by filter paper

Should contain ionic salt to allow ions to move but not one that will interfere w half cells

Eg potassium chloride cant be used w solution of silver nitrate

Signs of electrode potential values

Negative sign shows polarity to hydrogen, flow from neg to positive

Standard potential is measure whe. No electrons are flowing so both half cells are in equilibrium

Measuring standard electrode potential of systems involving gases

Different oxidation states

EMF definition

The electromotive force is the standard electrode potential of a half cell, measured under standard conditions of 298K, 100kPa, and conc of 1mol-3 connected to a standard hydrogen electrode

How to calculate e cell

Reduction - oxidation

How are electrode potentials listed as an electrochemical series

At the top, theres the most negative e so the equilibrium lies furthest to the left and it is best at releasing electrons and forming ions

At the bottom theres the most postitve e so equilibrium lies furthest to the right and it is reluctant to release electrons and form ions

Predicting feasibility

-the thermodynamic feasibility of a chemical reaction can be predicted using standard electrode potentials positive = feasible

However, a reaction may be thermodynamically feasible but might not take place because the reactants might be kinetically stable so the activation energy would be large and it would not take place at standard conditions pr it might not be taking place under standard conditions

Changing conditions may alter position of eq so the half cell changes and it might be feasible