Define electrochemical series and write its two applications.

Answer:

Electrochemical series: The arrangement of electrodes (half reactions) in the order of their standard reduction potentials is called the electrochemical series. Electrodes with highly negative E° (e.g. Li, K) are at the top and those with highly positive E° (e.g. F₂) are at the bottom, with the standard hydrogen electrode (E° = 0) in between.

Applications:

1. Relative strength of oxidising and reducing agents: the higher the E° (reduction potential), the stronger the oxidising agent (e.g. F₂); the lower the E°, the stronger the reducing agent (e.g. Li).
2. Calculation of standard emf of a cell: E°_cell = E°_cathode − E°_anode, using values from the series.
3. Predicting the feasibility of a redox reaction: a reaction is spontaneous if E°_cell calculated for it is positive. Also, a metal with lower E° displaces a metal with higher E° from its salt solution, and metals above hydrogen liberate H₂ from dilute acids.