c161l16_10_13 - Hess's Law, the 1st Law again Most of what...

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

View Full Document Right Arrow Icon
Hess Hess s Law, the 1 s Law, the 1 st st Law again Law again W Most of what we need to know about enthalpy is a consequence of 2 properties It’s extensive It’s a state function W Let’s see what that means Extensive A B B Δ H=a H=a 2A 2A 2B 2B Δ H=2a H=2a State function AB C Δ H 1 Δ H 2 Δ H 3 = Δ H 1 + Δ H 2
Background image of page 1

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

View Full DocumentRight Arrow Icon
Other statements of Hess Other statements of Hess s s Law Law W The enthalpy of a reaction is the same whether the reaction occurs in one step or 100 steps. W The enthalpy of a reaction is equal to the sum of the enthalpies of the steps into which a reaction can be divided W The sum of enthalpies around any cycle is exactly zero. W These are all statements of the first law: conservation of energy
Background image of page 2
Example Example W A sample of 23.0g of CH 3 CH 2 OH required 22 kJ to vaporize. What is its enthalpy of vaporization? molsCH 3 CH 2 OH = 23.0 g×1mol/46.07g = 0.499 mol Δ H vap = 22kJ/ 0.499 mol = 44.1 kJ/mol
Background image of page 3

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

View Full DocumentRight Arrow Icon
Example Example W Given the following thermodynamic data, find
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 12

c161l16_10_13 - Hess's Law, the 1st Law again Most of what...

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