Final answer:
To find the molality of an NaCl solution with a mole fraction of 0.100 for NaCl, calculate the number of moles of water in 1.0 kg, and then use the number of moles of NaCl and H2O to find the molality.
Step-by-step explanation:
The student is asking about the molality of a NaCl solution with a given mole fraction. To calculate molality, we need to know the number of moles of solute and the mass of the solvent in kilograms. Given that the mole fraction of NaCl is 0.100, the mole fraction of water will be 0.900. Since the molar mass of water (H2O) is 18g/mol, we can find the number of moles of water by using the mole fraction formula which involves the numerator being the moles of NaCl and the denominator being the moles of the solvent (water) plus the moles of NaCl (0.100 = 3.0 mol NaCl / (3.0 mol NaCl + moles of water)). You then solve for the moles of water and convert the mass of water to kilograms to find the molality of the NaCl solution.