Lacey_Che131_S2012_Lect-13s

Lacey_Che131_S2012_Lect-13s - State Function State...

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Lec-13: Enthalpy; Heating Curves Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 1 State Function State functions play an py Important role in thermodynamics Why is the state function so important ? Distance between two cities is a state function , but distance aveled is a ath function Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 2 traveled is a path function State Functions The internal energy E is a tate function state function Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 3 First law of thermodynamics ` Δ E = q + w Δ E = change in system’s internal energy q = heat w = work ` Work done by the system = P Δ V ( P is the atmospheric pressure and Δ V is the change in volume). Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 4
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First law of thermodynamics A battery plus a motor constitutes a system. The system does 555 kJ of work and releases 124 kJ of heat. What is the change in the Internal Energy of the system ? nergy loss reduces the internal energy =q+w = (-124 - 555 ) kJ = -679 kJ Energy loss reduces the internal energy of the system U=q+w = (-124 - 555 ) kJ = -679 kJ The internal energy of the system ecreases by 679 kJ Δ decreases by 679 kJ Constant Constant Volume; Volume; Δ E = q Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 5 PV Work Compressed helium is used to inflate balloons on a day when the atmospheric pressure is 1.01 atm. If each balloon is inflated from an initial volume of 0.0 L to a final volume of 4.8 L, how much P–V work is done by 100 balloons on the surrounding atmosphere when they are inflated? ` The balloons and the helium they contain are the ystem system.
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This note was uploaded on 03/29/2012 for the course CHE 131 taught by Professor Kerber during the Spring '08 term at SUNY Stony Brook.

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Lacey_Che131_S2012_Lect-13s - State Function State...

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