How much NaCl is required to make 100 ml of a 2% solution?

To prepare a 2% NaCl solution, the concentration indicates that there are 2 grams of NaCl per 100 milliliters of solution. This percentage is calculated using the formula:

[ \text{Mass of solute (g)} = \text{Percentage (%) } \times \text{Volume of solution (mL)} / 100

]

Substituting the values for a 2% solution in 100 mL gives:

[ \text{Mass of NaCl} = 2 \times 100 / 100 = 2g ]

Therefore, to achieve the desired concentration of 2%, you need to dissolve 2 grams of NaCl in enough water to make the total volume equal to 100 mL. This is why the correct answer is 2 grams.