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Question
A system releases 130 kJ of heat while 109 kJ of work is done on the system. Calculate the change in internal energy.
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Solution
Data: Q = −130 kJ, W = −109 kJ
Find: ΔU = ?
Calculations:
ΔU = Q − W
ΔU = −130 − (−109)
ΔU = −130 + 109
ΔU = −21 kJ
∴ The change in internal energy is −21 kJ. This is the change (decrease) in the internal energy.
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