The decomposition of ammonium nitrate (NH4NO3) is an endothermic reaction, absorbing heat and causing a temperature decrease. The dissolution of calcium chloride (CaCl2) in water is an exothermic reaction, releasing heat and causing a temperature increase.
The reactions provided can be categorized based on whether they are endothermic or exothermic.
1. NH4NO3 (s) → NH4+ (aq) + NO3- (aq) + heat:
This reaction involves the decomposition of ammonium nitrate (NH4NO3) into ammonium ions (NH4+) and nitrate ions (NO3-) in an aqueous solution, accompanied by the absorption of heat. The temperature increases as heat is absorbed during the reaction, indicating an endothermic process. Endothermic reactions absorb energy from the surroundings, resulting in a decrease in temperature in the immediate environment.
2. CaCl2 (s) + 2 H2O → Ca(OH)2 (aq) + 2 HCl (g) + heat:
This reaction represents the dissolution of calcium chloride (CaCl2) in water to form calcium hydroxide (Ca(OH)2) and hydrogen chloride gas (HCl), releasing heat. The liberation of heat signifies an exothermic reaction. Exothermic reactions release energy into the surroundings, leading to an increase in temperature in the immediate environment.