Fluoride concentration in drinking water is 1.5 ppm. What is the approximate mass of fluoride in 2 L water if density of water is taken as 1 g per mL?
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Answer and explanation
Correct answer: 3.0 mg
For a dilute aqueous solution with density approximately 1 kg L−1, 1 ppm by mass corresponds approximately to 1 mg solute per litre of water. Thus 1.5 ppm corresponds to about 1.5 mg L−1. In 2 L, fluoride mass = 1.5 × 2 = 3.0 mg. The density assumption is what permits this convenient ppm-to-mg/L approximation.
Frequently asked questions
What is the correct answer to this question?
3.0 mg
Why is this the correct answer?
For a dilute aqueous solution with density approximately 1 kg L−1, 1 ppm by mass corresponds approximately to 1 mg solute per litre of water. Thus 1.5 ppm corresponds to about 1.5 mg L−1. In 2 L, fluoride mass = 1.5 × 2 = 3.0 mg. The density assumption is what permits this convenient ppm-to-mg/L approximation.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
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