chemistry
posted by mike .
a sample of seawater has a density of 1.02kg/L and has the following ion in parts per million by mass, 19,000 Cl. how do you find the molar concentration of the ion?

19,000 ppm by mass means
19,000 g Cl^/1,000,000 g solution.
The solution then consists of 19,000 g Cl^ and 981,000 g H2O.
Remember that molarity = moles/L.
How many moles do you have.
19,000 g Cl^/atomic mass Cl^ = moles.
What is the volume of water? That is
mass = volume x density. You have density and mass, calculate volume, convert to liters and use in the moles/L formula. 
Thank You Dr. Bob, I really appreciate your help