1. Understand Dilution

Dilution is the process of reducing the concentration of a solution by adding more solvent (in this case, water). The key principle is that the amount of solute (NaCl) remains the same, but it's distributed in a larger volume.

2. Calculate the Moles of NaCl

* Molarity (M) = moles of solute / liters of solution

* We have 25.0 mL of a 6.0 M NaCl solution, which is 0.025 L.

* Rearranging the formula: moles of NaCl = Molarity x Liters

* moles of NaCl = 6.0 M x 0.025 L = 0.15 moles

3. Calculate the Final Volume

* Initial volume = 25.0 mL

* Added volume = 100 mL

* Final volume = 25.0 mL + 100 mL = 125 mL = 0.125 L

4. Calculate the Final Concentration

* Molarity (M) = moles of solute / liters of solution

* Molarity = 0.15 moles / 0.125 L = 1.2 M

Therefore, the final concentration of the NaCl solution is 1.2 M.