A research team studies a hydrated salt that undergoes two sequential processes when added to water at room temperature:
Process 1 (0 s → 45 s): The solid dissolves completely. The temperature of the solution decreases from 23.0∘C to 18.0∘C.
Process 2 (45 s → 120 s): The anhydrous ions produced in Process 1 react exothermically with liquid water to form a hydrated complex. During this interval the temperature of the solution rises from 18.0∘C to 30.0∘C.
Assume the total mass of the solution remains 120.0g throughout, its specific heat capacity is constant at 4.0Jg−1∘C−1, and heat exchange with the external environment is negligible.
(1) Calculate the heat q1 (in joules) associated with Process 1 and state its sign.
(2) Calculate the heat q2 (in joules) associated with Process 2 and state its sign.
(3) Determine the overall heat change qoverall for the combined processes and indicate whether, on net, the system absorbs or releases heat.
(4) Explain how the sequential temperature profile allows you to classify each individual process as endothermic or exothermic without performing calculations.
(5) If the experiment were repeated in a poorly insulated container that permitted a constant heat loss of 1500J to the surroundings during the 120 s period, predict qualitatively how the observed minimum and maximum temperatures would differ from those reported above. Justify your answer.