How do you calculate ΔSfus and ΔSvap for HCl given melting point,ΔHfus, boiling point, and ΔHvap

Question

also how do you determine the entropy change when 5.20 mol of HCl(l) freezes at atmospheric pressure.

Answer 1

dG = dH-TdS. At the melting point, dG = 0 (dG always 0 at equilibrium conditions)
rearrange to dS = dH/T..
Boiling point don the same way but substitute dHvap for dHfus and different T.

Answer 2

For #2, I assume you have tables.
HCl(l) ==> HCl(s)
dSrxn = dSproduct - dSreactant
That will give you dS/mol, then multiply by 5.20 mols.