This assignment focuses on Pore size of membranes measurement. There is also a description of Calculating the activity coefficient of the water.
Pore size of membranes measurement : Calculating the activity coefficient of the water
Answer all questions please A(i) (3 marks) The pore size of membranes can be measured by using the decrease in vapour pressure of liquid nitrogen condensed in the pores (i.e. cavities) at low temperatures. Calculate the diameter of the pores in a membrane if at 80.0 K the pressure of N2 gas above the membrane is measured to be 1.310 bar. At 80.0 K liquid nitrogen has the following properties: = 8.27 mN m-1 Vm = 3.528 x10-5 m3 mol-1 p*vap = 1.369 bar (ii) (2 marks) Water droplets adhere weakly to lotus leaves and but strongly to rose petals, but in both cases the contact angle is ~150o. Explain, with the aid of diagrams Bi) The partial pressure at 25 °C of the water vapour above a water-ethanol solution for which x(H2O) = 0.5 is 3.7 kPa. The total vapour pressure is 8.7 kPa.