If the work is done by the system on the surroundings and heat is absorbed by the system from the surroundings the change in internal energy E will be
Correct answer: B. E = q+(-w)
- A. E = q+w
- B. E = q+(-w)
- C. E= (-q)+(-w)
- D. E = (-q)+w
Explanation
According to the first law of thermodynamics:ΔE=q+wq = heat absorbed by the system (positive if absorbed, negative if released)w= work done on the system (positive if surroundings do work on the system, negative if system does work on surroundings)Now in this question:The system absorbs heat → q=+qThe system does work on surroundings → w= −w So,ΔE=q+(−w)ΔE=q−w
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About Thermochemistry and Energetics of Chemical Reactions
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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