Chapter%208

Chapter%208 - 8.8(a The quantities H vap and S vap can be...

This preview shows pages 1–2. Sign up to view the full content.

8.8 (a) The quantities vap vap and H S Δ ° Δ ° can be calculated using the relationship vap vap 1 ln H S P R T R Δ ° Δ ° = − + Because we have two temperatures with corresponding vapor pressures (we know that the vapor pressure = 1 atm at the boiling point), we can set up two equations with two unknowns and solve for vap vap and H S Δ ° Δ ° . If the equation is used as is, P must be expressed in atm, which is the standard reference state. Remember that the value used for P is really activity that, for pressure, is P divided by the reference state of 1 atm so that the quantity inside the ln term is dimensionless. vap 1 1 vap vap 1 1 vap 8.314 J K mol ln 1 311.6 K 13 Torr 8.314 J K mol ln 760 Torr 227.94 K H S H S Δ ° × = − + Δ ° Δ ° × = − + Δ ° which give, upon combining terms, 1 1 1 vap vap 1 1 1 vap vap 0J K mol 0.003209K 33.9 J K mol 0.004 3871K H S H S = − × Δ ° + Δ ° = − × Δ ° + Δ ° Subtracting one equation from the other will eliminate the vap S Δ ° term and allow us to solve for vap : H Δ ° 1 1 1 vap 1 vap 33.9 J K mol 0.001178 K 28.8 kJ mol H H + = + × Δ ° Δ ° = + (b) We can then use vap H Δ ° to calculate vap S Δ ° using either of the two equations: 1 1 vap 1 1 vap 1 1 1 1 vap 1 1 vap 0 0.003 209 K ( 28 800 J mol ) 92.4 J K mol 33.9 J K mol 0.004 3871K ( 28 800 J mol ) 92.4 J K mol S S S S

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

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/30/2012 for the course CHEM 6B taught by Professor Crowell during the Spring '08 term at UCSD.

Page1 / 5

Chapter%208 - 8.8(a The quantities H vap and S vap can be...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online