10. POTENTIAL ENERGY DIAGRAMS A C + heat  A + B ENDOTHERMIC ∆ H is POSITIVE. A. PE of reactants B. PE of products C. PE of activated complex D. activation energy (for forward reaction, E act ) E. Heat of Reaction, ∆H, Enthalpy F. activation energy for reverse reaction B C D reactants products transition state activated complex E F

12. PE DIAGRAMS with CATALYST

13. SPONTANEOUS REACTIONS What makes a reaction SPONTANEOUS ? decreasing exothermic increasing s -> l -> g more randomness increasing endothermic decreasing g -> l -> s less randomness endothermic decreasing g -> l -> s less randomness exothermic increasing s -> l -> g more randomness NOT SPONTANEOUS ENTROPY ENTHALPY depends on the temperature SPONTANEOUS

20. A (s) + 2B (g) C (s) + D (g) + heat   stress volume of gas must decrease volume of gas must increase NO SHIFT NO SHIFT catalyst decrease temp. increase temp. decrease pressure increase pressure decrease conc. of C decrease conc. of B increase conc. of D increase conc. of A

21. LE CHATELIER’S PRINCIPLE The rates of both the forward and reverse reactions are increased by the same amount. NO SHIFT add a catalyst more heat/ energy needs to be produced to make up for the loss towards heat/ energy exothermic reaction is favored decrease temperature of system extra heat/ energy must be used up away from heat/ energy exothermic reaction is favored increase temperature of system for gas : pressure decrease = volume increase towards more moles of gas decrease pressure of system for gas : pressure increase = volume decrease towards fewer moles of gas increase pressure of system need to produce more of substance to make up for what was removed towards substance decrease concentration of a substance extra concentration needs to be used up away from substance increase concentration of a substance WHY? SHIFT STRESS

23. activated complex reactants products

24. N 2(g) + 3H 2(g)  2NH 3(g) + 22.0 kcal  10. Decrease press. 9. Increase press. 8. Decrease temp 7. Increase temp 6. Remove NH 3 5. Remove H 2 4. Remove N 2 3. Add NH 3 2. Add H 2 1. Add N 2 [NH 3 ] [H 2 ] [N 2 ] Shift Stress

25. N 2(g) + 3H 2(g)  2NH 3(g) + 22.0 kcal  _____ _____ _____ _____ _____ _____ 10. Decrease press. 9. Increase press. 8. Decrease temp 7. Increase temp 6. Remove NH 3 5. Remove H 2 4. Remove N 2 3. Add NH 3 2. Add H 2 1. Add N 2 [NH 3 ] [H 2 ] [N 2 ] Shift Stress

26. 2CO 2(s) + heat 2CO (s) + O 2(g)   stress catalyst is added temp. is decreased temp. is increased pressure is decreased pressure is increased O 2 is added CO is removed O 2 is added CO is added CO 2 is added

30. 12.6 kcal + H 2(g) + I 2(g)  2HI  10. Decrease press. 9. Increase press. 8. Decrease temp 7. Increase temp 6. Remove HI 5. Remove I 2 4. Remove H 2 3. Add HI 2. Add I 2 1. Add H 2 [HI] [I 2 ] [H 2 ] Shift Stress

31. 12.6 kcal + H 2(g) + I 2(g)  2HI  _____ _____ _____ _____ _____ _____ = = NO CHANGE REMAINS THE SAME 10. Decrease press. 9. Increase press. 8. Decrease temp 7. Increase temp 6. Remove HI 5. Remove I 2 4. Remove H 2 3. Add HI 2. Add I 2 1. Add H 2 [HI] [I 2 ] [H 2 ] Shift Stress

35. QUIZ 

37. NaOH (s)  Na + (aq) + OH - (aq) + 10.6 kcal  8. Decrease press 7. Increase press 6. Decrease temp 5. Increase temp 4. Add H + (removes OH + ) 3. Add KOH (adds OH - ) 2. Add NaCl (adds Na + ) 1. Add NaOH [OH - ] [Na + ] NaOH (s) Shift Stress

38. NaOH (s)  Na + (aq) + OH - (aq) + 10.6 kcal  _____ _____ _____ _____ NO EFFECT …………………… REMAINS THE SAME 8. Decrease press 7. Increase press 6. Decrease temp 5. Increase temp 4. Add H + (removes OH + ) 3. Add KOH (adds OH - ) 2. Add NaCl (adds Na + ) 1. Add NaOH [OH - ] [Na + ] NaOH (s) Shift Stress

43. The water gained 350 calories of heat and the metal lost 350 calories of heat.

44. 1. PE of reactants 2. PE of products 3. PE of activated complex 4. activation energy 5. Heat of Reaction, ∆H 6. activation energy of reverse reaction EXOTHERMIC REACTION ENDOTHERMIC REACTION 1 Reaction Coordinate Energy 2 3 4 5 6 1 2 3 4 5 6 Reaction Coordinate Energy When a catalyst is added, 2 , 3 , and 6 are lowered.