1. b 2. e 3. ad 4. ae 5. bc 6. ac 7. a 8. c 9. d 10. ab 11. b 12. b 13. b 14. b 15. a 16. b 17. d 18. b 19. c 20. d 21. b 22. b 23. a
Problems:
24. 81 kJ
25. (a) exothermic since the temperature of the surrounding water increased. (b) 6,745 J or 6.7 kJ. (c) -324 kJ/mol
26. DG = -137 kJ; This reaction is spontaneous since DG is negative.
27.
(a) DS
is negative since CO2 changes from the very disordered gaseous state
to ordered solid state.
(b) DS
is again negative since two moles of gases turn into one mole of solid.
This change corresponds to an increase in order and a decrease in disorder and
entropy.
(c) DS
is positive since the water is warmed. At higher temperatures particles of
any substance move around faster and are less ordered so entropy increases.
28.
(a) DG
< 0 since reaction is spontaneous; DS
< 0 since aqueous ions become solid precipitate. This change
corresponds to a drop in entropy and therefore, DS
is negative. DH
is negative. Since the DS
change is unfavorable and the reaction is spontaneous, DH
must be negative to make the overall reaction spontaneous.
(b) DG
< 0; since the reaction occurs, this means that the forward reaction is
spontaneous. DH
> 0; since the reaction feels cold in the surroundings, this means that the
change was endothermic with a positive DH.
DS
is positive because a solid ionic compound breaks up into aqueous ions which
have less order and more entropy. Also since DG
< 0 and DH
is unfavorable, the DS
must be significantly positive to drive the spontaneity of the reaction.
