A student prepared a stock solution by dissolving 20.0 g of KOH in enough water to make 150.0 mL of solution. She then took 15.0 mL of the stock solution and diluted it with enough water to make a final solution of 65.0 mL. What is the concentration of the final solution in mol/L?

Calculate the concentration of the stock solution in mol/L by dividing the number of moles of KOH by the volume of the stock solution in liters (150.0 mL converted to liters).

Use the dilution formula \( C_1V_1 = C_2V_2 \) to find the concentration of the final solution, where \( C_1 \) is the concentration of the stock solution, \( V_1 \) is the volume of the stock solution used (15.0 mL), \( C_2 \) is the concentration of the final solution, and \( V_2 \) is the final volume (65.0 mL).