Calculate the mass percentage of 15 ppm of chloroform (CHCl3) in water. (1) 15×10⁻⁴ (2) 15×10⁻³ (3) 15×10⁻⁶ (4) 15×10⁻²
Answer (1)
To calculate the mass percentage of chloroform (CHCl₃) in water at 15 ppm (parts per million), we need to understand what ppm means.
1 ppm means 1 part of a substance per one million parts of the solution. In terms of mass, 1 ppm is equivalent to 1 milligram of a substance per kilogram of solution, which can also be equivalently expressed as 1 gram per 1,000,000 grams of the solution.
Now, we have 15 ppm, which means there are 15 parts of chloroform per million parts of the solution. Therefore:
Mass percentage = mass of solution (1,000,000 parts) mass of solute (15 parts) × 100
That calculates to:
Mass percentage = 1 , 000 , 000 15 × 100 = 0.0015%
Thus, the mass percentage of 15 ppm of chloroform in water is 15 × 1 0 − 4 %.
Therefore, the correct multiple-choice option is (1) 15 × 1 0 − 4 .
