18 g glucose is dissolved in 90 g water. If the molar mass of glucose is 180 g mol−1, what is the molality?
Answer and explanation
Correct answer: About 1.11 mol kg−1
Molality is defined as moles of solute per kilogram of solvent, not per kilogram of solution. Glucose moles = 18 g / 180 g mol⁻¹ = 0.10 mol, while water mass = 90 g = 0.090 kg. Thus molality = 0.10 / 0.090 = 1.11 mol kg⁻¹ approximately, making A correct. B omits division by solvent mass, and C and D use incorrect values.
Frequently asked questions
What is the correct answer to this question?
About 1.11 mol kg−1
Why is this the correct answer?
Molality is defined as moles of solute per kilogram of solvent, not per kilogram of solution. Glucose moles = 18 g / 180 g mol⁻¹ = 0.10 mol, while water mass = 90 g = 0.090 kg. Thus molality = 0.10 / 0.090 = 1.11 mol kg⁻¹ approximately, making A correct. B omits division by solvent mass, and C and D use incorrect values.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
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