Final answer:
The correct chemical equation for water reacting with potassium oxide to form potassium hydroxide is B) H_2O + K2O → 2KOH.
Step-by-step explanation:
The chemical equation that shows the product of water reacting with potassium oxide is B) H_2O + K2O → 2KOH. This reaction represents the formation of potassium hydroxide when water reacts with potassium oxide - an alkali metal oxide, which is typically a basic oxide. Potassium oxide reacts with water to form a base, here potassium hydroxide (KOH), and this type of reaction is characteristic of metal oxides reacting with water, demonstrating their basic properties.