When ammonium chloride (NH_4Cl) dissolves in water, the temperature of the solution decreases. Is this process endothermic or exothermic?

• A. Endothermic
• B. Neither endothermic nor exothermic
• C. Exothermic
• D. Both endothermic and exothermic

Answer: (A)

Verified step by step guidance

1. Understand the definitions: An endothermic process absorbs heat from the surroundings, causing the surroundings to cool down, while an exothermic process releases heat to the surroundings, causing the surroundings to warm up.
2. Analyze the observation: When ammonium chloride (NH_4Cl) dissolves in water, the temperature of the solution decreases, meaning the solution and its surroundings lose heat.
3. Relate temperature change to heat flow: A decrease in temperature indicates that heat is absorbed by the dissolving process from the water, which means the system (NH_4Cl dissolving) takes in heat.
4. Conclude the type of process: Since heat is absorbed during the dissolution, the process is endothermic.
5. Summarize: The dissolution of NH_4Cl in water is an endothermic process because it requires heat input, which results in a temperature drop in the solution.