(a) The balanced chemical equation for the reaction that is prevented by storing potassium metal under kerosene is:
2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g)
In this reaction, potassium (K) reacts with water (H₂O) to form potassium hydroxide (KOH) and hydrogen gas (H₂).
(b) The type of chemical reaction that is prevented by storing potassium metal under kerosene is a metal-water reaction. In this specific case, it's a highly reactive metal (potassium) reacting with water to produce a metal hydroxide (potassium hydroxide) and hydrogen gas. Storing the potassium under kerosene prevents its exposure to atmospheric moisture (water), which can lead to a violent and potentially dangerous reaction. The kerosene forms a barrier that prevents contact between the potassium and water, thus ensuring the metal remains safely stored.