Question

The average concentration of chloride ions (molar mass = 34.353) in seawater is 19.353 grams per kilogram. The maximum allowable concentration of chloride ion in drinking water is 250 ppm by mass. How many times as much chloride ion is there in seawater than the maximum amount allowed in safe drinking water?

How do I compare them? Would I convert them to moles? or can I compare them by mass?

Answer 1

I remember that 1 ppm = 1 mg/L and since 1L has a mass of 1000g (at least for dilute solutions) that will be 1 mg/kg.
You have 19.353g or 19353 mg/kg so you must have 19,353 ppm. You should be able to take it from here.

Let's see if that checks out.
? ppm = (g solute/g solvent)*1E6
?ppm = (19.353g/1000 g solvent)*1000 = 19353 ppm. Yep, it checks.

Answer 2

19,103