In general, ?S is positive if: (1) more gas moles are produced than reacted. (2) a solid turns into a liquid or gas (3) a liquid turns into a gas (4) a solid dissolves (5) there are more product moles than reactant moles (6) the temperature of a substance is increased So with those guidelines in mind: (a) 2NO(g) + O2(g) --> 2NO2(g) I suspect ?S would be negative because 3 gas moles become 2 gas moles. (b) 2KClO3(s) --> 2KCl(s) + 3O2(g) ?S would be positive in this case because 2 moles of solid reactant produce 2 moles of solid product and 3 moles of gaseous products. (c) Cl2(g) (100ºC, 1 bar) --> Cl2(g) (10ºC, 1 bar) ?S should be negative in this case; as the temperature decreases so does the entropy of the system. (d) NaClO3(s) --> Na^+1(aq) + ClO3^-1(aq) ?S is positive because a solid substance is dissolving. (e) C3H8(g) + 5O2(g) --> 3CO2(g) + 4H2O(g) ?S is positive because 6 moles of gaseous reactants become 7 moles of gaseous products. I hope that helps. Good luck! Solution In general, ?S is positive if: (1) more gas moles are produced than reacted. (2) a solid turns into a liquid or gas (3) a liquid turns into a gas (4) a solid dissolves (5) there are more product moles than reactant moles (6) the temperature of a substance is increased So with those guidelines in mind: (a) 2NO(g) + O2(g) --> 2NO2(g) I suspect ?S would be negative because 3 gas moles become 2 gas moles. (b) 2KClO3(s) --> 2KCl(s) + 3O2(g) ?S would be positive in this case because 2 moles of solid reactant produce 2 moles of solid product and 3 moles of gaseous products. (c) Cl2(g) (100ºC, 1 bar) --> Cl2(g) (10ºC, 1 bar) ?S should be negative in this case; as the temperature decreases so does the entropy of the system. (d) NaClO3(s) --> Na^+1(aq) + ClO3^-1(aq) ?S is positive because a solid substance is dissolving. (e) C3H8(g) + 5O2(g) --> 3CO2(g) + 4H2O(g) ?S is positive because 6 moles of gaseous reactants become 7 moles of gaseous products. I hope that helps. Good luck!.

1. In general, ?S is positive if: (1) more gas moles are produced than reacted. (2) a
solid turns into a liquid or gas (3) a liquid turns into a gas (4) a solid dissolves (5) there are more
product moles than reactant moles (6) the temperature of a substance is increased So with those
guidelines in mind: (a) 2NO(g) + O2(g) --> 2NO2(g) I suspect ?S would be negative because 3
gas moles become 2 gas moles. (b) 2KClO3(s) --> 2KCl(s) + 3O2(g) ?S would be positive in
this case because 2 moles of solid reactant produce 2 moles of solid product and 3 moles of
gaseous products. (c) Cl2(g) (100ºC, 1 bar) --> Cl2(g) (10ºC, 1 bar) ?S should be negative in
this case; as the temperature decreases so does the entropy of the system. (d) NaClO3(s) -->
Na^+1(aq) + ClO3^-1(aq) ?S is positive because a solid substance is dissolving. (e) C3H8(g) +
5O2(g) --> 3CO2(g) + 4H2O(g) ?S is positive because 6 moles of gaseous reactants become 7
moles of gaseous products. I hope that helps. Good luck!
Solution
In general, ?S is positive if: (1) more gas moles are produced than reacted. (2) a
solid turns into a liquid or gas (3) a liquid turns into a gas (4) a solid dissolves (5) there are more
product moles than reactant moles (6) the temperature of a substance is increased So with those
guidelines in mind: (a) 2NO(g) + O2(g) --> 2NO2(g) I suspect ?S would be negative because 3
gas moles become 2 gas moles. (b) 2KClO3(s) --> 2KCl(s) + 3O2(g) ?S would be positive in
this case because 2 moles of solid reactant produce 2 moles of solid product and 3 moles of
gaseous products. (c) Cl2(g) (100ºC, 1 bar) --> Cl2(g) (10ºC, 1 bar) ?S should be negative in
this case; as the temperature decreases so does the entropy of the system. (d) NaClO3(s) -->
Na^+1(aq) + ClO3^-1(aq) ?S is positive because a solid substance is dissolving. (e) C3H8(g) +
5O2(g) --> 3CO2(g) + 4H2O(g) ?S is positive because 6 moles of gaseous reactants become 7
moles of gaseous products. I hope that helps. Good luck!