Question
Predict whether Fe^3+ can oxidize I- to I2 under standard-state conditions.
Explanation / Answer
Fe3+ + 2I- I2 + 2Fe2+ It can be split into two half equations: 1. 2Fe3+ + 2e- --> 2Fe2+ Standard reduction potential: +0.771 V 2. 2I- --> I2 + 2e- Standard reduction potential: -0.536 V Thus, the overall standard reduction potential is +0.235 V and thus >0 thus, the delta G < 0 and the reaction can occur (upon applying a minimum voltage of 0.235 V The Gibb's free energy is negative according to delta G = -nFE Where n = no. of electrons involved in the equation, F = the Faraday constant = 96,485 Coulumb mol^-1, and E = the overall standard reduction potential I do not have a clear idea of the second part of your question. However, if you are asking for the ease of determining if the reaction can proceed by the two means, then my answer is that using the electrochemical method is easier, as: 1. It does not involve any apparatus apart from a piece of paper, a writing medium and a calculator; 2. The value K, equilibrium constant, is easily found using very simple calculations, and the constants, e.g. the reduction potentials are very easily obtained from the internet. 3. There might be experimental errors in the chemical approach, although it is not likely in this experiment (the equilibrium is an extreme tilt towards the products) Hope these help. Btw give a thumbs up if you can =P