Describe the preparation of a 250 mL 102 ppm solution of salicylic acid in water

The maximum allowable amount of nitrate, measured as nitrogen, in drinking water is 10.0 ppm (by mass). Calculate the correponding molarity of the nitrate ion.

The US EPA's regulatory limit for mercury (Hg) in drinking water is 2.0 ppb. A 255 L water sample was acquired from a lake and found to contain 2.3 ppb of Hg. How many grams of mercury are there in the water sample?

What is the concentration of mercury in ppm if there are 321.4 μg mercury ions in a 4.50 L of water?