6-section

# 6-section - 1 6. Macroscopic Chemical Kinetics (Chapter 18)...

This preview shows pages 1–4. Sign up to view the full content.

1 6. Macroscopic Chemical Kinetics (Chapter 18) Chemical kinetics is concerned with understanding how fast chemical reactions occur, and why and how those rates vary with temperature, pressure, and the amounts of the component reagent species present. How do we characterize reaction rates ? Consider the combustion of ethylene: C 2 H 4 (g) + O 2 (g) CO 2 (g) + H 2 O(g) [ begin by balancing the reaction ! ] We can describe the rate in terms of: how fast the C 2 H 4 disappears, or how fast the O 2 is used up, or how fast the CO 2 is produced, or how fast the H 2 O is produced. We usually characterize rates in terms of the time derivative of the concentration of some selected reagent or product species. For reagents being produced (species on the R.H.S. of the equation), those derivatives have numerical values, since For reagents being consumed (species on the L.H.S. of the equation), those derivatives have values,

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

View Full Document
2 e.g., for the ethylene combustion reaction considered above, occurring in a closed container, consider a plot of the concentrations of all species vs. time. 0 20 40 60 80 100 time concentration We want to deFne ‘reaction rate’ as a positive quantity, so we write: { R ate } = d [C 2 H 4 ] dt = d [O 2 ] dt =+ d [C O 2 ] dt d [H 2 O ] dt More generally, for an arbitrary reaction n 1 A+ n 2 B n 3 C+ n 4 D+ n 5 E in which n i are the stoichiometric coeﬃcients of the balanced equation { R ate } = d [A] dt = d [B] dt = d [C] dt = d [D] dt = d [E] dt
3 e.g., for the reaction 2 Fe 3+ (aq) + Sn 2+ (aq) 2Fe 2+ (aq) + Sn 4+ (aq) In general, the rate of reaction changes with time.

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 09/28/2011 for the course CHEM 350 taught by Professor Prof.djasd during the Winter '10 term at Waterloo.

### Page1 / 12

6-section - 1 6. Macroscopic Chemical Kinetics (Chapter 18)...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online