9.15

[Sarah Rutzick 1L]

For 9.15 part a, the answer book gives the heat of fusion as -6.01 kJ/mol. How do we know that the heat of fusion should be negative?

[Ammar Amjad 1L]

The book gives the heat of fusion of water as 6.01 kj.mol^-1, meaning thats how much energy is required to go from solid to liquid water. However, the question is asking you to calculate the entropy for the freezing of water; therefore, you would use negative heat of fusion, because that's how much energy the system will release.

[Rachel Formaker 1E]

Heat is always required to melt a substance, so ∆H is positive.

Heat is released when a substance freezes, so ∆H is negative.

∆H_freezing = ∆H_fusion, and since you are given ∆H_fusion from Table 8.3, you just reverse the sign of ∆H_fusion to get ∆H_freezing = -6.01 kJ/mol

[Manvir2K]

How do you get -6.01 kJ/mol or 4.35 kJ/mol from appendix 2A?