If 5 g of a non-dissociated solute produces a molality of 0.25 m in 0.2 kg of solvent, what is the molar mass of the solute?
Answer and explanation
Correct answer: 100 g mol^-1
Molality is defined as moles of solute per kilogram of solvent. Therefore, the number of solute moles is n = 0.25 mol kg^-1 × 0.2 kg = 0.05 mol. Molar mass is the mass of solute divided by the number of moles, so M = 5 g/0.05 mol = 100 g mol^-1. The non-dissociation condition confirms that the given molality corresponds directly to the solute formula units. Thus, option C is correct.
Frequently asked questions
What is the correct answer to this question?
100 g mol^-1
Why is this the correct answer?
Molality is defined as moles of solute per kilogram of solvent. Therefore, the number of solute moles is n = 0.25 mol kg^-1 × 0.2 kg = 0.05 mol. Molar mass is the mass of solute divided by the number of moles, so M = 5 g/0.05 mol = 100 g mol^-1. The non-dissociation condition confirms that the given molality corresponds directly to the solute formula units. Thus, option C is correct.
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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