## Chemistry: The Molecular Science (5th Edition)

20. ppb=$\frac{20\,\mu g}{kg}=\frac{20\,\mu g}{L}$ (as 1 kg water has volume 1 L) $=\frac{0.020\,mg}{L}$ This concentration is higher than the acceptable limit. (Acceptable limit=0.015 mg/L) 0.0030 ppm=$\frac{0.0030\,mg}{kg}=\frac{0.0030\,mg}{L}$ This concentration is lower than the acceptable limit.