A reaction occurs in a closed, frictionless piston–cylinder apparatus. During the reaction the system loses 200 kJ of heat to the surroundings and does 45 kJ of work on the surroundings by expansion.
(a) Determine the sign (positive or negative) of ΔE for the system.
(b) Based on your result, classify the reaction as endothermic or exothermic and justify your choice in one sentence.