Which of the following correctly describes the dissolution of potassium sulfide (K2S) in water?

• A. K2S is insoluble in water because sulfide salts are generally insoluble.
• B. K2S is soluble in water because all potassium salts are soluble.
• C. K2S partially dissolves in water, forming a precipitate.
• D. K2S reacts with water to form potassium hydroxide and hydrogen sulfide gas.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the solubility rules for ionic compounds in water. Generally, all potassium (K⁺) salts are soluble in water regardless of the anion they are paired with.
2. Step 2: Recognize that potassium sulfide (K₂S) is an ionic compound composed of potassium ions (K⁺) and sulfide ions (S²⁻). Since potassium salts are soluble, K₂S should dissolve in water.
3. Step 3: Consider the behavior of the sulfide ion (S²⁻) in water. Sulfide ions can react with water to some extent, producing hydroxide ions (OH⁻) and hydrogen sulfide (H₂S) gas, but this is a secondary reaction and does not prevent the initial dissolution.
4. Step 4: Evaluate the options given: the statement that K₂S is insoluble is incorrect based on solubility rules; partial dissolution with precipitate formation is unlikely; and while K₂S can react with water, the primary description of dissolution focuses on solubility.
5. Step 5: Conclude that the best description is that K₂S is soluble in water because all potassium salts are soluble, which aligns with standard solubility rules.