Electrochemistry some concepts Reduction halfreaction Oxidizing agent e

Electrochemistry: some concepts Reduction halfreaction Oxidizing agent + νe- → Reducing agent Oxidant + νe- → Reductant Ox + νe- → Reducing agent → Oxidizing agent + νe- Oxidation halfreaction Reductant → Oxidant + νe. Red → Ox + νe- 1

Electrochemistry: some concepts Reduction halfreaction Total Oxidizing agent + νe- → Reducing agent Oxidant + νe- → Reductant Ox + νe- → Red Ox 1 + Red 2 + νe- → Red 1 + Ox 2 + νereaction Ox 1 + Red 2 → Red 1 + Ox 2 Reduction 1 Oxidation 2 5 x + 2

Electrochemistry: some concepts Ox 1 + Red 2 → Red 1 + Ox 2 But what about the reverse reaction? Red 1 + Ox 2 → Ox 1 + Red 2 Ox 2 + Red 1 → Red 2 + Ox 1 Electrochemical Equilibrium reaction → Will it run spontaneously to the right or to the left? → Where lies the equilibrium? 3

Consider the problem in an electrochemical cell -V Pt forms a ‘driving force’ + for the reaction, like Pt 4

Consider the problem in an electrochemical cell -V Pt forms a ‘driving force’ + for the reaction, like Pt Equilibrium: Relation between and 5

6

Electrochemical cells 7

Standard Electrochemical Potentials EΘ (@ 298 K) alphabetical order (Ed. 11: Table 6 D. 1 b) for all T(aq) 8

Standard Electrochemical Potentials EΘ (@ 298 K) electrochemical order (Ed. 11: Table 6 D. 1 a) 9

Standard Thermodynamic data (@ 298 K) (Ed. 11: Table 2 C. 7) for all T(aq) 10

Standard Thermodynamic data (@ 298 K) (Ed. 11: Table 2 C. 7) 11

12

Why p. H is defined via the activity 13

Why p. H is defined via the activity 14

Why p. H is defined via the activity Mixture with components A, B, C, …. . Definition of activity: 15

Activity as an effective concentration ideal or dilute behaviour deviation from ideal Molarity (mol/L): activity coefficient on the concentration scale 16

Alternative activity coefficients Molarity (mol/L): Molality (mol/kg): Mole fraction (): 17