A water sample has calcium ion concentration 40 ppm. What mass of calcium ions is present in 5 L of the sample?
Answer and explanation
Correct answer: 200 mg
For a dilute aqueous solution, 1 ppm is approximately 1 mg per litre because 1 L of water has a mass close to 1 kg. Thus, 40 ppm means about 40 mg of calcium ions per litre. For 5 L, mass = 40 mg L⁻¹ × 5 L = 200 mg. Therefore option C is correct; 40 mg ignores the volume multiplier and the larger values use an incorrect conversion.
Frequently asked questions
What is the correct answer to this question?
200 mg
Why is this the correct answer?
For a dilute aqueous solution, 1 ppm is approximately 1 mg per litre because 1 L of water has a mass close to 1 kg. Thus, 40 ppm means about 40 mg of calcium ions per litre. For 5 L, mass = 40 mg L⁻¹ × 5 L = 200 mg. Therefore option C is correct; 40 mg ignores the volume multiplier and the larger values use an incorrect conversion.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Some Basic Concepts of Chemistry. Topic: Mole concept and molar mass.
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