# Explain how this can be accounted for by the change in the multiplicity when the ethanol goes from a liquid to a gas.

1. Consider the system of 46g (1 mole) sample of liquid ethanol at 1bar of pressure in aan open beaker on a cold hot plate in a lab that is 20C . Given the data below explain the conditions that must occur for the sample to convert from the liquid to the gas. C2H5OH (lq) C2H5OH (vap) The enthalpy (∆H) for this conversion is a measure of how much energy it takes to break the bonds between the ethanol molecules in order to change their phase. If we assume that the heat capacity is constant over the temperatures we are discussing the enthalpy change will be constant. a. Why is ∆S positive for this conversion? Explain how this can be accounted for by the change in the multiplicity when the ethanol goes from a liquid to a gas. b. At the melting point (352K) the entropic driving force must just balance the enthalpic staying power (ie ). If the hotplate is turned on to a very low heat and the ethanol is warmed just to 79C and maintained at that temperature what will happen? Describe the molecular process within the beaker of ethanol but also explain the change in the entropy of the surroundings that must happened to warm the ethanol. c. Fill in the values in the following table: Using the relationships: , for equilibrium processes and for spontaneous processes. Although the ethanol will not vaporize at temperature below its boiling point you can still calculate the entropy changes at this temperature as well as above by creating a thermodynamic cycle. 363K ∆H◦ ∆Ssurr ∆Ssys ∆Stot 352K 342K