Help me please. Substance S° (J/mol ×K) Al (s) 28.33 Al2O3 (s) 50.92 Cl2 (g) 223
ID: 1045121 • Letter: H
Question
Help me please.
Substance S° (J/mol×K)
Al (s)
28.33
Al2O3 (s)
50.92
Cl2 (g)
223.07
H2 (g)
130.68
N2 (g)
191.61
O2 (g)
205.14
Si (s)
18.83
SiCl4 (g)
330.73
SiHCl3 (g)
330.73
SiH2Cl2 (g)
285.71
SiH3Cl (g)
313.87
SiH4 (g)
204.62
Si3N4 (s)
101.3
SiO2 (s)
41.84
1. Explain the signs and relative magnitudes of these values. Why are they all positive?
2. What kinds of substances have higher S° values? lower S° values?
3. Why do the standard entropies of gases tend to be higher than those of solids?
Thank you!
Al (s)
28.33
Al2O3 (s)
50.92
Cl2 (g)
223.07
H2 (g)
130.68
N2 (g)
191.61
O2 (g)
205.14
Si (s)
18.83
SiCl4 (g)
330.73
SiHCl3 (g)
330.73
SiH2Cl2 (g)
285.71
SiH3Cl (g)
313.87
SiH4 (g)
204.62
Si3N4 (s)
101.3
SiO2 (s)
41.84
Explanation / Answer
1. a +ve entropy of a substance means the compound is stable in the present form. Higher value of standard entropy sugest greater degree of freedom or randomness and is in the order solid < liquid < gases.
2. Solids having less degree of randomness have lower So value compared to freely moving gaseous molecules or systems.
3. Gas molecules are kept apart at much greater distance from each other and so they can move more freely as compared to solids where the molecules are kept very close to each other. Less distance does not let molecules to move as freely as in gaseous ststems and theus So values seen in the table above are lower fro solids than gas.
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