flow. Temperature is an intensive property of matter, while heat is an extensive property … effect on the standard reduction potential because it is an intensive property. The number … calculated from standard reduction potentials, ^ standard reduction potential is the voltage produced

value because the standard electrode potential is an intensive property. During operation of an electrochemical cell, chemical energy is transformed into Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change. These reactions involve electrons moving via an electronically conducting phase (typically an external electric circuit, but not necessarily, as in electroless plating) between electrodes separated by an ionically conducting and electronical E°(Cu2+/Cu) = 0.34 V Changes in the stoichiometric coefficients of a balanced cell equation will not change the E°red value because the standard electrode potential is an intensive property. Cathode: Na+(aq) + e− → Na(s) E°red = –2.71 V Anode: 2 Cl−(aq) → Cl2(g) + 2 e− E°red = +1.36 V Cathode: 2 H2O(l) + 2 e− → H2(g) + 2 OH−(aq) E°red = –0.83 V Anode: 2 H2O(l) → O2(g) + 4 H+(aq) + 4 e− E°red = +1.23 V Reaction 1 is discarded as it has the most negative value on standard reduction potential thus making it less thermodynamically favorable in the process. When comparing the reduction potentials in reactions 2 and 4, the oxidation of chloride ion is favored over oxidation of water, thus chlorine gas is produced at the anode and not oxygen gas. Although the initial analysis is correct, there is another effect, known as the overvoltage effect. Additional voltage is sometimes required, beyond the voltage predicted by the E°cell. This may be due to kinetic rather than thermodynamic considerations. In fact, it has been proven that the activation energy for the chloride ion is very low, hence favorable in kinetic terms. In other words, although the voltage applied is thermodynamically sufficient to drive electrolysis, the rate is so slow that to make the process proceed in a reasonable time frame, the voltage of the external source has to be increased (hence, overvoltage). The overall reaction for the process according to the analysis is the following:

\end{align*} \] Voltage is an Intensive Property Standard reduction potential is an intensive property, meaning that changing the stoichiometric coefficient in a half reaction does not affect the value of the standard potential. For example, Oxidation:{Al(s) → Al3+(aq) +3e-} x 2 is still Eo= -1.676 Reduction:{Sn2+(aq) +2e- → Sn(s)} x 3 is still Eo= -0.137 If the stoichiometric coefficient is multiplied by 2, the standard potential does not change: Calculate the cell potential in the following redox reaction under standard conditions: \[\ce{ Fe^{3+} (aq) + V^{2+} (aq) \rightarrow Fe^{2+} (aq) + V^{3+}(aq)} \nonumber \] Solution Consult the table of standard reduction potentials (Table P1) for each half reaction: \[Fe^{3+}_{(aq)}+e^- \rightarrow Fe^{2+}_{(aq)} \;\;\;\; \text{with } E^o=0.771\; V \nonumber \] \[V^{2+}_{(aq)} \rightarrow V^{3+}_{(aq)} + e^- \;\;\;\; \text{with } E^o=-0.255\; V \nonumber \] The cell potential is \[E^o_{cell}=E^o_{cathode}-E^o_{anode}=0.771\; V -(-0.255\; V)=1.026 \; V \nonumber \] Glossary - Anode: Electrode in an electrochemical cell on which the oxidation reaction occurs.