Why doesn't potassium ion K+ from KMnO4 appear in the following two unbalanced equations: MnO4– + C2O42– Mn2+ + CO2
MnO4– + Fe2+ Mn2+ + Fe3+ ?
A. KMnO4 is not added to either reaction.
B. K+ is a spectator ion and redox reactions are written as net ionic reactions.
C. The presence of K+ would result in a net positive charge in the products.
D. The equations cannot be balanced if the potassium ion K+ is present.
E. None of these.
K^+ is a spectator ion and that is why is isn't in the equation. The part of answer B I don't like is "and redox reactions are written as net ionic reactions." That implies that redox reactions are never written as molecular equation and that isn't true. Therefore, technically, E is the only correct answer but the spirit of the question may call for B to be the correct answer.
The correct answer is B. K+ is a spectator ion and redox reactions are written as net ionic reactions.
In the given unbalanced equations, KMnO4 is not explicitly mentioned as a reactant or product. However, KMnO4 is a compound that dissociates in water to form K+ and MnO4- ions.
In redox reactions, we typically focus on the changes in oxidation states of the elements involved. The potassium ion, K+, does not undergo any change in oxidation state in these reactions. It remains in its +1 oxidation state throughout.
Spectator ions are ions that are present in the reaction mixture but do not participate in the reaction itself. They remain in the same oxidation state and do not undergo any chemical change. In this case, K+ is a spectator ion because it remains unchanged throughout the reactions.
When writing net ionic equations for redox reactions, spectator ions are usually omitted. The focus is on the ions and molecules that are actually undergoing a change in oxidation state. Therefore, the K+ ion is not included in the net ionic equations for these reactions.
So, option B is the correct answer because K+ is a spectator ion and redox reactions are written as net ionic reactions.