Lecture 4, First Law Calc 1-14-08

Lecture 4 First - Example – Gas heated at constant volume 10.0 liters of helium gas at STP heated to 375 K at constant V Calculate ∆ E Closed

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Example – Gas heated at constant volume 10.0 liters of helium gas at STP heated to 375 K at constant V. Calculate ∆ E Closed System 10.0 liters He 273 K 1.00 atm q is + Surroundings 375 K heat, q Initial State Closed System 10.0 liters He 375 K P increases Δ E is + Surroundings 375 K Final State mol K J 47 . 12 R 2 3 C v ⋅ = ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = V V q E w w q E = = + = Δ Δ Example – Gas heated at constant volume Calculation of ∆ E NOTE: CHANGES ARE ALWAYS CALCULATED AS FINAL – INITIAL ∆T = T(FINAL) – T(INITIAL) ∆E = E(FINAL) – E(INITIAL) ( ) ( ) ( ) J q E J q K K mol K J mol q T nC q mol l mol l He of mol V V V v V 568 568 273 375 47 . 12 446 . 446 . 4 . 22 00 . 1 . 10 = = Δ = − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⋅ = Δ = = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = Write this down for future reference to constant pressure process Heat capacities of gases at constant volume 32.0 Br 2 12.5 Xe 24.1 Cl 2 12.5 Kr 19.9 N 2 12.5 Ar 20.2 CO 12.5 Ne 20.18 H 2 12.5 He C v ( J K-1 mol-1 ), Diatomic gas C v ( J K-1 mol-1 ), Monatomic gas Internal Energy and Temperature • Heat capacities, q and Δ E 1 mole of He, C v = 12.5 J/K·mol T initial = 298 K 1 mole H 2 , C v = 20.18 J/K·mol T initial = 298 K q=25 J q=40.36 J He, T final = 300 K Δ E = 25 J H 2 , T final = 300 K Δ E = 40.36 J Constant V Constant V Δ T is the same for both processes, but heating He by 2 K requires less energy than heating H 2 by 2 K....
View Full Document

This note was uploaded on 08/06/2008 for the course CHEM 1B taught by Professor Watts during the Winter '08 term at UCSB.

Page1 / 18

Lecture 4 First - Example – Gas heated at constant volume 10.0 liters of helium gas at STP heated to 375 K at constant V Calculate ∆ E Closed

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online