ppm is also called as parts per million. This means that one out a million.  This unit is commonly used to measure of concentration of something in water.

1ppm = 1mg per liter of solution OR

          = 1mg per 1kg of solution

In the problem we have 1.4ppm Chlorine which also means that it has 1.4mg of Chlorine in 1L of solution.

to solve for the amount of Chlorine present in 250mL of water:

1. convert the unit of volume of water

          1000mL = 1 L

          250 mL x ( 1L/1000mL) = .250 L

2. multiply the volume of water to the concentration of Chlorine (1.4 mg/L)

          1. 4 mg/L x .250L = .35 mg Chlorine

3. convert mg chlorine to g chlorine

          1000 mg = 1g

          .35mg x ( 1 g / 1000mg) = 0.00035 g chlorine

4. show your answer in scientific notation

          3.5x10^-4 grams chlorine