A water desalination plant is set up near a salt marsh containing water that is 0.20 M NaCl?

For ionic solutions, the osmotic pressure is P = iMRT, where P is osmotic pressure, M is molarity, R the universal gas constant equal to 0.082057 L�atm/(K�mol) and T the temperature. i takes the value of 2 in the NaCl solution. The temperature is 22�C, equal to (273.15K + 22K)=295.15K. Then. P = 2 * 0.20M * 0.082057 L*atm*(K*mol) * 295.15K = 9.6876atm, which is rounded to 9.7atm. It's the osmotic pressure of the solution, but too the minimun pressure to allow reverse osmosis.