1 / 18

Reaction Spontaneity

Reaction Spontaneity. How can a fire start on its own? (without a spark). Spontaneous Reaction. Occurs naturally and favors formation of products 4Fe(s) + 3O 2 (g)  2Fe 2 O 3 (s) ΔH = -1625 kJ CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 O(l) ΔH = -891 kJ. Nonspontaneous Reaction.

glain
Download Presentation

Reaction Spontaneity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Reaction Spontaneity How can a fire start on its own? (without a spark)

  2. Spontaneous Reaction • Occurs naturally and favors formation of products 4Fe(s) + 3O2(g)  2Fe2O3(s) ΔH = -1625 kJ CH4(g) + 2O2(g)  CO2(g) + 2H2O(l) ΔH = -891 kJ

  3. Nonspontaneous Reaction Does not favor formation of products 2Fe2O3(s)  4Fe(s) + 3O2(g) ΔH = 1625 kJ CO2(g) + 2H2O(l)  CH4(g) + 2O2(g) ΔH = 891 kJ H2O(s)  H2O(l) ΔH = 6.01 kJ

  4. Some endothermic reactions are SPONTANEOUS!

  5. ENTROPY (S) • The measure of disorder or randomness of particles in a system LAW OF DISORDER Spontaneous processes always increase the entropy of a system

  6. Law of Disorder

  7. Changes in Entropy (ΔS) • Δssystem= Sproducts–Sreactants

  8. 1. Changes in State

  9. 2. The dissolving of a gas in a solvent always results in a decrease in entropy. CO2(g)  CO2(aq) Δssystem < 0

  10. 3. Assuming no change in physical state, the entropy increases when: # of product particles > # of reactant particles. 2SO3(g)  2SO2(g) + O2(g) Δssystem > 0

  11. 4. when a solid or a liquid dissolves to form a solution. NaCl(s)  Na+(aq) + Cl-(aq) Δssystem > 0

  12. 5. increase in the temperature increase in entropy

  13. Does entropy increase or decrease? CaCO3 (s)  CaO (s) + CO2 (g) NH3 (g) + HCl (g)  NH4Cl (s)

  14. How ΔHsystem and ΔSsystemaffect reaction spontaneity

  15. Gibb’s Free Energy!! ΔGsystem = ΔHsystem– TΔSsystem The energy that is available to do work (useful energy)

  16. ΔGsystem and reaction spontaneity

  17. Is the following reaction spontaneous? N2(g) + 3H2(g)  2NH3(g) ΔH°system= -91.8 kJΔS°system= -197 J/K ΔGsystem = ΔHsystem– TΔSsystem

  18. For a process, ΔHsystem=145 kJ and ΔSsystem=322J/K. Is the reaction spontaneous at 382 K?

More Related