# CHEM

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Calculate ΔSfus and ΔSvap for HF.
Determine the entropy change when 7.60 mol of HF(l) freezes at atmospheric pressure.

I already calculated ΔSfus as 24.103 J/k*mol and ΔSvap as 86.07 J/K*mol....These are correct (I checked them already). I need help with this part of the question:
Determine the entropy change when 7.60 mol of HF(l) freezes at atmospheric pressure.

I got an answer of 183.18 J/K and it marked me wrong and said "The value of ΔSfus above is for 1.00 mol of HF. You need to scale that value up for 7.60 mol of HF. Also, consider the sign of your answer. Does freezing result in an increase or decrease in entropy?"

• CHEM -

never mind I got it....the answer is -183.18 J/K

• CHEM -

How did you get that? I'm stuck on getting to 183.18

• CHEM -

Freezing is the opposite of melting, so reverse the ΔSfus. ΔSfus is in units of (J/K*mol). Multiply that by 7.6 mol. That should give you the right answer.

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