According to the EPA, the maximum contaminant level (MCL) of thallium in drinkin

Question

According to the EPA, the maximum contaminant level (MCL) of thallium in drinking water is 0.0020 mg/L.

(a) Convert the MCL of thallium from milligrams per liter to parts per billion (ppb).

(b) A farmer has recently dug a new well for his property. He sends a 12.0 mL sample of the well water to the EPA to be tested for the presence of thallium. What is the maximum amount of Tl (in g) that can be present in this 12.0 mL sample based on its MCL?

(c) Suppose the farmer has rethought his plan and dug a new well on the other side of his property. He sends a new 12.0 mL sample. After testing, the EPA determines that the sample of water contains 0.00169 g/mL Tl. Is the well water safe to consume?

Explanation / Answer

(a) Here, 1 mg / L = 1000 micro g/L = 1000 ppb

Therefore, 0.0020 mg/L = 0.0020x1000 = 2.0 ppb

(b) Again, maximum amount of T1 in micrograms = Vol. in mL x concentration of T1 in ppb

= 12.0 x 2.0 = 24.0 micro g.

(c) Concentration of T1 = 0.00169 micro g/mL = 0.00169 / 1000 mg / L = 1.69 x 10^-6 mg/L

And this is less than the safe drinking water level which is 0.0020 mg/L

Therefore, the well water is safe to consume.

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