Warming solid ammonium chloride () with aqueous sodium hydroxide in an open test tube is an example — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

The reaction produces ammonia gas ($NH_4Cl + NaOH \rightarrow NaCl + NH_3 + H_2O$). Because the test tube is open, the $NH_3$ gas escapes, allowing the exchange of both matter and energy with the surroundings. This defines an open system.