Confused about single displacement Reaction [closed]








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This question is about predicting reactions


Al(s) + FeO(s) ---> no reaction


Al is higher on the activity series so why does it result in no reaction instead of replacing Fe?




Although the electrode potential of the reaction:


$$\ce{2Al(s) + 3 Fe^2+(aq) -> 2Al^3+(aq) + 3 Fe (s) }$$


is favorable (E0 = +1.21 V), which is what I am assuming you are referring to, it does not apply in this instance as it takes place in aqueous solution. Although the reaction of *solid* aluminum with *solid* ferrous oxide is thermodynamically favorable, it is not kinetically favorable. The Fe2+ ions are locked in a lattice with O2- ions, and solid aluminum normally has a protective oxide coating on it that prevents it from oxidation. However, because the reaction is thermodynamically favorable, it will actually proceed at a very slow rate (but only if the aluminum oxide layer is removed). This rate is almost impossible to detect, and there is no reaction for all intents and purposes.


When in aqueous solution, Fe2+ ions could technically be formed and the above equation could apply in this case; however, this will not occur in this situation as FeO is insoluble in water. If the ferrous salt used instead was soluble, such as FeCl2, then the reaction could occur in aqueous solution, and iron will precipitate out of solution.


The only way for the reaction to take place with the given states of matter is for a thermite reaction to take place:


$$\ce{2Al(s) + 3 FeO(s) -> Al2O3(s) + 3 Fe (s) }$$


However, the only way for this to occur is for the reaction system to be ignited, which is not a given condition in your equation.


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