{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lacey_Che131_S2012_Lect-13s

# Lacey_Che131_S2012_Lect-13s - State Function State...

This preview shows pages 1–3. Sign up to view the full content.

h l Lec-13: Enthalpy; Heating Curves Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 1 State Function State functions play an Important role in thermodynamics Why is the state function so important ? Distance between two cities is a state function , but distance traveled is a path function Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 2 traveled is a State Functions The internal energy E is a state function Roy A. Lacey, Stony Brook University; Che 131, Spring 2012 3 First law of thermodynamics ` Δ E = q + w E h i Δ = 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

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
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 ? Energy loss reduces the internal energy U=q+w = (-124 - 555 ) kJ = -679 kJ Energy loss reduces the internal energy of the system Δ The internal energy of the system decreases by 679 kJ decreases by 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 system system. ` ` Volume change ( Δ V) as all the balloons are inflated is 100 balloons × 4.8 L/balloon = 480 L The work ( w ) done by the system Work is done by the system on its surroundings.
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}