Expressing Concentration Using Parts Per Million

If you wanted to prepare 1 L of a 10 ppm solution of zinc, Zn, you would weigh out 10 mg of zinc metal, place it in a 1-L flask, dissolve it, and dilute to the 1-L mark with distilled water. If you need to prepare a volume other than 1 L, the parts per million (ppm) concentration is multiplied by the volume in liters  

Tell how you would prepare 500 mL of a 25 ppm copper solution from pure copper metal. Solution 5.8 

Weigh 12.5 mg of copper into a 500-mL flask, dissolve (in dilute nitric acid), and dilute to the mark with water. 

Another example of the preparation of parts per million solutions is by dilution. It is a very common practice to purchase solutions of metals that are fairly concentrated (1000 ppm) and then dilute them to obtain the desired concentration. This is done to save solution preparation time in the laboratory. As per the discussion in Chapter 4, (see Equation (4.14) and the accompanying discussion), the concentration is multiplied by the volume both before and after dilution. Using the parts per million unit, we have 

How would you prepare 100 mL of a 20 ppm iron solution from a 1000 ppm solution  

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