Question 9.11: The maximum allowable concentration of chloroform, CHCl3, in...

Fundamentals of General, Organic, and Biological Chemistry

The maximum allowable concentration of chloroform, $CHCl_3$ , in drinking water is 100 ppb. What is the maximum amount (in grams) of chloroform allowed in a glass containing 400 g (400 mL) of water?
ANALYSIS We are given a solution amount (400 g) and a concentration (100 ppb). This concentration of 100 ppb means

100  ppb = \frac{Mass  of  solute  (g)}{Mass  of  solution  (g)} \times 10^9

This equation can be rearranged to find the mass of solute.
BALLPARK ESTIMATE A concentration of 100 ppb means there are $100 \times 10^{-9} g (1 \times 10^{-7} g)$ of solute in 1 g of solution. In 400 g of solution, we should have 400 times this amount, or $400 \times 10^{-7} g = 4 \times 10^{-5} g$ .

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