To raise the temperature of 2 moles of a diatomic gas by 1°C at constant pressure, the required amount of heat is 120 cal. The amount of heat which goes as the gas's internal energy is almost:
Correct answer: C. 85.2 Cal
- A. 82.5 Cal
- B. 80 Cal
- C. 85.2 Cal
- D. 58.8 Cal
Explanation
Option C is correct as Cp and CV for a diatomic gas are 7/2 R and 5/2 R respectively. The gas's internal energy is increased by only 0.71 of the supplied energy. The rest is used to do work against external pressure. 0.71 ×120 = 85.2 Cal
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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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