Question

Local rivers and lakes are tested regularly for toxins. One of the toxins of great concern is lead. The maximum amount of lead allowed in water to be considered safe is 15 ppb (parts per billion). A routine test of a local lake determined the concentration of the lead in the lake was 3.32 x 10^-7 M. Is the water in the lake above or below the allowed limit? What is the concentration of the lead in the lake in ppb?

Answer 1

3.32 * 10 ^ -7 M

or 3.32 * 10^-7 moles / litre

mass per liter = moles * molar mass

= 3.32*10^-7 * 207

= 6.8724*10^-5 g / litre

multiply by 10^6

= 68.724 ppb

above the limit

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