Two percent by weight of NaCl solution is prepared. The molality of this solution is:

0.35 mol

The correct answer is option 1. 0.35 mol.

The molality of a solution can be calculated using the formula:

\( \text{Molality} = \frac{\text{moles of solute}}{\text{mass of solvent (in kg)}} \)

In the given question, we have a 2% (W/W) NaCl solution. This means that the mass of the solute (NaCl) and the mass of the solution are both in grams. Specifically, 2% NaCl solution implies that 2 grams of NaCl is present in 100 grams of the solution.

The solution consists of a solute (NaCl) and a solvent (water). Given the values of the solute and the solution, we can calculate the mass of the solvent. Thus, the mass of the solvent will be:

\(\text{mass of solvent} = \text{mass of solution} - \text{mass of solute} = 100 \, \text{g} - 2 \, \text{g} = 98 \, \text{g} = 0.098 \, \text{kg} \)

Next, we need to calculate the number of moles of NaCl. The given mass of NaCl is 2 grams, and the molecular mass of NaCl is:

\( \text{molecular mass of NaCl} = 23 + 35.5 = 58.5 \)

Thus, the number of moles can be calculated as:

\( \text{moles of NaCl} = \frac{\text{mass of NaCl}}{\text{molecular mass of NaCl}} = \frac{2 \, \text{g}}{58.5} \approx 0.034 \)
Finally, we can calculate the molality of the solution using the formula mentioned earlier:
\( \text{Molality} = \frac{\text{moles of NaCl}}{\text{mass of solvent}} = \frac{0.034}{0.098} \approx 0.35 \, \text{m} \)
Hence, the molality of the given solution is 0.35 m.