Question

which of the following is not spontaneous process at 25 degrees celsius and 1 atm pressure?

ice melting
iron rusting
salt dissolving
steam condensing
water boiling

Answer 1

I think what you must do here is to calculate dSsurroundings + dSsystem and see if it is + or - dS (or you can go through dG = dH - TdS and see if the rxn is + or - dG.
I assume you can find dH and S in your text. For
H2O: S for ice is about 20 but you need to confirm that. S for liquid water is about 70 so dS for the system is about +50 (70-20= +50)
dSsurounding = -dHrxn/T = -6000J/298 = about -20 J/mol.
dStotal = dSsurr + dSsys = -20J + 50 = +30. Since it is + the system is spontaneous. The others are done the same way.