Which of the following statements is incorrect?
Correct answer: C. In the equation ΔE = q - PΔV, where q = ΔV.
- A. ΔH is positive for endothermic reactions.
- B. ΔH is negative for exothermic reactions.
- C. In the equation ΔE = q - PΔV, where q = ΔV.
- D. All the above are correct.
Explanation
Option C is the correct answer because it contains an incorrect statement. The equation ΔE = q - PΔV is used to calculate the change in internal energy of a system, where q represents heat added to the system, and PΔV is the work done by the system. The statement 'where q = ΔV' is incorrect because q represents heat, not a change in volume. Options A and B are correct as they accurately describe the nature of endothermic and exothermic reactions, respectively. Option D is incorrect because it claims all statements are correct, which they are not.
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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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