For a reaction delta h= -286 kj. when is the reaction spontaneous a: when t delta s = 2(-286 kj) b: when t delta s= -286 kj c: when t delta s < -286 kj d: when t delta s > 0

The answer is d.potassium

Remember that rust prevented by placing a sacrificial electrode in electrical contact with the iron. the sacrificial electrode must be composed of a metal that  oxidizes  more easily than iron (that is, it must be below iron in table 18.1).