{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

5_60_lecture6

5_60_lecture6 - MIT OpenCourseWare http/ocw.mit.edu 5.60...

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

MIT OpenCourseWare http://ocw.mit.edu 5.60 Thermodynamics & Kinetics Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .

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

View Full Document
5.60 Spring 2008 Lecture #6 page 1 Thermochemistry Goal: To predict Δ H for every reaction, even if it cannot be carried out in the laboratory The heat of reaction Δ H rx is the Δ H for the isothermal reaction at constant pressure. e.g. Fe 2 O 3 (s, T,p ) + 3H 2 (g, T,p ) = 2Fe(s, T,p ) + 3H 2 O( l , T,p ) ( , ) = 2 Fe ( T p ) + 3 H O 2 ( T p ) 3 H 2 ( T p , ) H 2 3 ( , ) Δ H rx T p H , H , H Fe O T p [ Δ H = H ( products ) H ( reactants ] ) rx We cannot know H values because enthalpy, like energy, is not measured on an absolute scale. We can only measure differences in enthalpy. Define a reference scale for enthalpy H (298.15K, 1 bar) 0 For every element in its most stable form at 1 bar and 298.15K H H ° 2 (g) ( 298.15 K ) = 0 e.g. The “ ° ” means 1 bar H C ° (graphite) ( 298.15 K ) = 0 Δ H f ° ( 298.15 K ) : We can now write reactions to form every compound from its constituent atoms. The heat
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 5

5_60_lecture6 - MIT OpenCourseWare http/ocw.mit.edu 5.60...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online