In a coffee-cup calorimeter, 100.0 g of H2O and 100.0 mL of HCl are mixed. The HCl had an initial temperature of 44.6 oC and the water was originally at 24.6 oC. After the reaction, the temperature of both substances is 31.3 oC.
a. Was the reaction exothermic or endothermic?Explain.
b. Calculate how much heat the water lost or gained.

(a). For water the reaction is Endothermic & for HCL the reaction is Exothermic.

(b). The heat gain by the water is Q = 2.814 KJ

Explanation:

Given data

Mass of water = 100 gm

Initial temperature of HCL = 44.6 °c

Initial temperature of water = 24.6 °c

Final temperature of both substances = 31.3 °c

(a). For water the reaction is Endothermic because the temperature of water is increases during the mixing process.

But for HCL the reaction is Exothermic because the temperature of HCL is decreases.

(b). Heat gain by water is given by

Q = 0.1 × 4.2 × (31.3 - 24.6)

Q = 2.814 KJ

Therefore the heat gain by the water is Q = 2.814 KJ