1. Place the following in order of decreasing standard molar entropy. H2O (l) H2
ID: 911443 • Letter: 1
Question
1. Place the following in order of decreasing standard molar entropy. H2O (l) H2O (g) H2O (s)
A) H2O (g) > H2O (l) > H2O (s)
B) H2O (s) > H2O (l) > H2O (g)
C) H2O (g) > H2O (s) > H2O (l)
D) H2O (l) > H2O (s) > H2O (g)
E) H2O (s) > H2O (g) > H2O (l) 2.
For the following example, identify the following.
H2O (l) H2O(s)
A) a negative H and a positive S
B) a positive H and a negative S
C) a negative H and a negative S
D) a positive H and a positive S
E) It is not possible to determine without more information.
3. Calculate S°rxn for the following reaction. The absolute entropies, S°, for each of the species are shown below the reaction. C2H2(g) + 2 H2(g) C2H6(g) S°(J/mol·K) 200.9 130.7 229.2
A) +303.3 J/K B) +560.8 J/K C) -102.4 J/K D) -233.1 J/K E) 229.2 J/K
4. Which of the following processes have a Ssys > 0?
A) 2 NH3(g) + CO2(g) NH2CONH2(aq) + H2O(l)
B) sodium chloride dissolves in pure water
C) 2 HBr(g) H2(g) + Br2(l)
D) lithium fluoride forms from its elements
E) All of the above processes have a S > 0.
5. Below what temperature does the following reaction become nonspontaneous? 2 HNO3(aq) + NO(g) 3 NO2(g) + H2O(l) H = +136.5 kJ; S = +287.5 J/K
A) 39.2 K
B) 151 K
C) 475 K
D) This reaction is nonspontaneous at all temperatures. E) This reaction is spontaneous at all temperatures.
Explanation / Answer
1. Place the following in order of decreasing standard molar entropy. H2O (l) H2O (g) H2O (s)
A) H2O (g) > H2O (l) > H2O (s)
B) H2O (s) > H2O (l) > H2O (g)
C) H2O (g) > H2O (s) > H2O (l)
D) H2O (l) > H2O (s) > H2O (g)
E) H2O (s) > H2O (g) > H2O (l)
2. For the following example, identify the following.
H2O (l) H2O(s)
A) a negative H and a positive S
B) a positive H and a negative S
C) a negative H and a negative S
D) a positive H and a positive S
E) It is not possible to determine without more information.
3. Calculate S°rxn for the following reaction. The absolute entropies, S°, for each of the species are shown below the reaction. C2H2(g) + 2 H2(g) C2H6(g) S°(J/mol·K) 200.9 130.7 229.2
S = (229)-(2*130 + 200) = -231
A) +303.3 J/K B) +560.8 J/K C) -102.4 J/K D) -233.1 J/K E) 229.2 J/K
4. Which of the following processes have a Ssys > 0?
A) 2 NH3(g) + CO2(g) NH2CONH2(aq) + H2O(l)
B) sodium chloride dissolves in pure water
C) 2 HBr(g) H2(g) + Br2(l)
D) lithium fluoride forms from its elements
E) All of the above processes have a S > 0.
5. Below what temperature does the following reaction become nonspontaneous? 2 HNO3(aq) + NO(g) 3 NO2(g) + H2O(l) H = +136.5 kJ; S = +287.5 J/K
G = H-TS
H-TS >0
H > TS
136500 > T*287.5
T< 136500/287.5 = 474.782
A) 39.2 K
B) 151 K
C) 475 K
D) This reaction is nonspontaneous at all temperatures. E) This reaction is spontaneous at all temperatures.
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