JEE Main levelSingle correct optionDifficulty 2 of 3td042
An exothermic reaction at constant pressure releases 92.2kJ of heat to a large surroundings at 298K (reversible heat exchange with the surroundings). The entropy change of the surroundings is
A+309.4JK−1
B−309.4JK−1
C+0.309JK−1
D+27476JK−1
Answer: A
ΔSsurr=−ΔHsys/T=92200/298=+309.4JK−1. The surroundings gain heat so their entropy rises. The 0.309 option forgets the kJ to J conversion.