Question

A chemist must prepare 550.0 mL of sodium hydroxide solution with a pH of 12.60 at 25°C. He will do this in three steps: Fill a 550.0 mL volumetric flask about halfway with distilled water. Weight out a small amount of solid sodium hydroxide and add it to the flask. Fill the flask to the mark with distilled water. Calculate the mass of sodium hydroxide that the chemist must weigh out in the second step. Round your answer to 2 significant digits.