A solution is prepared by dissolving 3.35 mol of NaCl in enough water to make 1.00 kg of solution. What is the mole fraction of NaCl (solute) in the solution?

• A. 0.943
• B. 0.335
• C. 0.057
• D. 0.0034

Answer: (C)

Verified step by step guidance

1. Identify the given information: moles of NaCl (solute) = 3.35 mol, and the total mass of the solution = 1.00 kg (which is 1000 g).
2. Calculate the moles of water (solvent) in the solution. First, find the mass of water by subtracting the mass of NaCl from the total mass of the solution. To do this, calculate the mass of NaCl using its molar mass (Na = 22.99 g/mol, Cl = 35.45 g/mol), then subtract from 1000 g.
3. Convert the mass of water to moles by dividing by the molar mass of water (approximately 18.015 g/mol).
4. Calculate the mole fraction of NaCl using the formula: \[ \chi_{\text{NaCl}} = \frac{n_{\text{NaCl}}}{n_{\text{NaCl}} + n_{\text{H_2O}}} \] where \(n_{\text{NaCl}}\) is the moles of NaCl and \(n_{\text{H_2O}}\) is the moles of water.
5. Substitute the values of moles of NaCl and moles of water into the mole fraction formula to find the mole fraction of NaCl in the solution.