What is the molarity of na + in a solution of nacl whose salinity is 5.6 if the solution has a density of 1.03 g/ml?

Salinity has units of grams NaCl or salt per kilogram solution. We can use the density given and the molar mass of the salt to convert from salinity to molarity. We do as follows:

(5.6 g / kg) (1.03 kg / L) (1 mol / 58.44 g) = 0.0987 mol NaCl / L