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+//example 6
+//obtaining fresh water from sea water
+clear
+clc
+Mw=18.0 //molar mass of water kg/kmol
+Ms=58.44 //molar mass of salt kg/kmol
+Rw=0.4615 //gas constant of pure water kJ/kg-K
+mfs=0.0348 //mass fraction of salt
+mfw=1-mfs //mass fraction of water
+Mm=1/((mfs/Ms)+(mfw/Mw)) //molar mass of mixture kg/kmol
+yw=mfw*Mm/Mw //mole fraction of water
+ys=1-yw //mole fraction of salt
+To=288.15 //Temp. of Seawater in kelvins
+Ru=8.314 //Universal Gas constant in kJ/kmol-K
+dm=1028 //density of seawater in kg/m^3
+wminin=-Ru*To*(yw*log(yw)+ys*log(ys)) //minimum work input required to separate 1 kg of seawater completely into pure water and pure salts kJ/kmol
+Wminin=wminin/Mm //minimum work input in kJ/kg seawater
+wminin2=Rw*To*log(1/yw) //minimum work input required to produce 1 kg of fresh water from seawater in kJ/kg fresh water
+Pm=dm*Rw*To*log(1/yw) //the minimum gauge pressure that the seawater must be raised if fresh water is to be obtained by reverse osmosis using semipermeable membranes in kPa
+printf("\n Hence, the mole fraction of water in the seawater is = %.4f. \n",yw);
+printf("\n Hence, the mole fraction of salt in the seawater is = %.2f percentage. \n",ys*100);
+printf("\n Hence, the minimum work input required to separate 1 kg of seawater completely into pure water and pure salts is = %.2f kJ/kg sea water. \n",Wminin);
+printf("\n Hence, the minimum work input required to produce 1 kg of fresh water from seawater kJ/kg fresh water is = %.2f kJ/kg fresh water. \n",wminin2);
+printf("\n Hence, the the minimum gauge pressure that the seawater must be raised if fresh water is to be obtained by reverse osmosis using semipermeable membranes is = %.0f kPa. \n",Pm); \ No newline at end of file