From each pair of substances below, choose the one with the higher
molar So, at 298 K
a) Hg (s), Hg (l) d) C2H6 (g), C2H4 (g)
b) HI (g), HCl (g) e) H2 (1 atm), H2 (2 atm), 1 mol at 298 K
c) NH3 (g), Ne (g) f) NaCl(s), NaCl (aq)
the answer is D C2H6(g)has a standard entropy of 206.5 and C2H4(g) has a standard entropy of 219.5 which are higher than all the other substances.
To determine which substance in each pair has the higher molar entropy (S), you need to consider the factors that affect entropy. One such factor is the state of matter, as different states have different levels of molecular disorder.
a) Hg (s) versus Hg (l): The entropy generally increases from solid to liquid. Thus, Hg (l) would have a higher molar entropy than Hg (s).
b) HI (g) versus HCl (g): The molar entropy of a gas depends on the complexity of its molecular structure. Since HI is a larger molecule than HCl, it is likely to have a higher molar entropy.
c) NH3 (g) versus Ne (g): Similar to the previous comparison, NH3 is a larger and more complex molecule than Ne. Therefore, NH3 is likely to have a higher molar entropy.
d) C2H6 (g) versus C2H4 (g): Both substances are gases, but C2H4 (ethylene) has a smaller molecular structure compared to C2H6 (ethane). A smaller, more simple molecule tends to have a lower molar entropy, so C2H6 is likely to have a higher molar entropy.
e) H2 (1 atm) versus H2 (2 atm), 1 mol: The molar entropy of a gas increases with higher pressure since the molecules are closer together. Therefore, H2 (2 atm) would have a higher molar entropy than H2 (1 atm).
f) NaCl (s) versus NaCl (aq): The entropy generally increases when a substance dissolves in a solvent, as the resulting solution has more molecular disorder. Thus, NaCl (aq) would have a higher molar entropy than NaCl (s).
Please note that these explanations are based on general principles and assumptions about entropy. In some cases, the actual values may vary depending on specific conditions.