Which of the following best describes a 1.00 m aqueous solution of NaCl?

• A. 1.00 mole of NaCl dissolved in enough water to make 1.00 liter of solution
• B. 1.00 mole of NaCl dissolved in 1.00 kilogram of water
• C. 1.00 mole of NaCl dissolved in 1.00 liter of water
• D. 1.00 mole of NaCl dissolved in enough water to make 1.00 kilogram of solution

Answer: (B)

Verified step by step guidance

1. Understand the definition of molality (m), which is the number of moles of solute dissolved per kilogram of solvent. It is expressed as \(m = \frac{\text{moles of solute}}{\text{kilograms of solvent}}\).
2. Recognize that the problem asks about a 1.00 m aqueous solution of NaCl, meaning the molality is 1.00 mol/kg, so there must be 1.00 mole of NaCl per 1.00 kilogram of water (the solvent).
3. Distinguish molality from molarity: molarity (M) is moles of solute per liter of solution, while molality (m) is moles of solute per kilogram of solvent. This difference is crucial for selecting the correct description.
4. Evaluate each option by checking whether it matches the molality definition: the correct description should specify 1.00 mole of NaCl dissolved in 1.00 kilogram of water, not in liters of solution or water.
5. Conclude that the best description of a 1.00 m NaCl solution is '1.00 mole of NaCl dissolved in 1.00 kilogram of water' because it aligns with the molality definition.