a routine test of a local lake determined the concentration of the lead in the lake was 3.32 * 10-7 m. is the water in the lake below or above the allowed limit?

Question

Local rivers and lakes are tested regularly for toxins. one of the toxins great concern is lead. the maximum amount of lead allowed in in water to be considered safe is 15ppb. a routine test of a local lake determined the concentration of the lead in the lake was 3.32 * 1-7 M. Is the water in the lake below or above the allowed limit? what is the concentration of the lead in the lake in ppb?

Answer 1

Atomic mass lead = 207 g/mole

3.32x10^-7 M = 3.32x10^-7 mole/L x 207 g/mol = 6.87x10^-5 g/L

6.87x10^-5 g/L x 1x10⁶ ug/g = 68.7 ug/L = 68.8 ppb = concentration of lead in the lake

This is ABOVE the allowed limit of 15 ppb