I have an exam on monday, for a course I'm not familiar with. I have studied the material and tried some example exam question but I can't seem to figure out how to get to the result of the following questions. Q1: 1. The problem statement, all variables and given/known data A sample of hydrogel is in equilibrium with a sodium chloride solution of 0.3 moles/l at T=298 K. The fixed charge density of the sample is −0.2 moleq/l. a. Calculate the osmotic pressure difference between the sample and the solution. 80 kPa b. Calculate the effective stress in the sample. 80 kPa 3. The attempt at a solution I tried it by calculating the Donnan-equilibrium concentrations but I have a feeling thats the wrong direction. Q2: A cylindrical hydrogel has homogenous, isotropic lineair elastic material properties. The sample is in equilibrium with a sodium chloride solution of concentration 0.15 Mol/l and of pressure zero, and is at temperature T= 300 K. The fixed charge density of the sample is −0.05 moleq/l. a. What is the pressure in the sample? 10 kPa b.What is the electrical potential difference between the sample and the solution? ξ = −4.3mV a. I started again with calculating the Donnan-equilibrium concentrations, but got stuck after that. b. No idea where to start. Thank in advance for anyone willing to help.