Given that one mole of Na+Cl− has a mass of 58.5 g, what would be the concentration of particles when 0.9 g of Na+Cl− is dissolved in 100 ml of water

D: the number of moles in 0.9 g = 0.9 g/58.5 g/mol = 0.0154 mole of Na+Cl−. However NaCl separates into ions when dissolved, so that there will be 0.0154 mol of Na and 0.0154 mol of Cl, hence 0.0308 osmol of particles = 30.8 mosmol per 100 ml. In one litre, the number of moles would be ten times greater, so 300 mosmol/L (is closest).