Answer to Question #283671 in Physical Chemistry for Willie

Question

 

 

 

3. (a) Estimate the melting point of ice (M=18.0 g/mol) under a pressure of 10 MPa. Assume that the mass density of ice under these conditions is approximately 0.915 g cm−3 and that of liquid water is 0.998 g cm−3. The entropy of fusion of water is 22.0 J K-1 mol−1at the normal melting point (0.1 Mpa).

(b) When a certain liquid (with M = 46.1 g mol−1) freezes at 1 bar and at −3.65 °C its mass density changes from 0.789 g cm−3 to 0.801 g cm−3. Its enthalpy of fusion is 8.68 kJ mol−1. Estimate the freezing point of the liquid at 100 MPa. (Hint: at equilibrium, △G=△H-T△S=0, △S=△H/T)

 

 

 

4. Dibromoethene (DE, p*DE = 22.9 kPa at 358 K) and dibromopropene (DP, p*DP = 17.1 kPa at 358 K) form a nearly ideal solution. If zDE = 0.60, what is (a) ptotal when the system is all liquid, (b) the composition of the vapor when the system is still almost all liquid?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answer 1

$\Delta\>T=\frac{T_f\>\Delta_p\>M}{\Delta_{fus}H}\>\>×\Delta(\frac{1}{p})$