A sample of drinking water was found to be severely contaminated with chloroform, `CHCl_(3)`, supposed to be carcinogen. The level of contamination was 15 ppm (by mass).
(i) Express this in per cent by mass.
(ii) Determine the molality of chloroform in the water sample.

Explanation

Let's solve the given problem step by step.

### Part (i): Express the contamination level in percent by mass

1. **Understand the given data**:
- Contamination level: 15 ppm (parts per million)
- This means 15 parts of chloroform in 1,000,000 parts of water by mass.

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