Final answer:
To calculate the mass of a 4.00% NaOH solution that contains 15.0 g of NaOH, you use the percentage by mass formula, which results in a mass of 375 g for the solution.
Step-by-step explanation:
To find the mass of a 4.00% NaOH solution that contains 15.0 g of NaOH, we set up a proportion based on the percentage by mass.
The formula for percentage by mass is:
Percentage by mass = (Mass of solute / Mass of solution) x 100%
So, for a 4.00% NaOH solution, the formula is:
4.00% = (15.0 g / Mass of solution) x 100%
By rearranging and solving for the mass of the solution, we find:
Mass of solution = (15.0 g / 4.00) x 100
Mass of solution = 375 g
Therefore, the mass of the NaOH solution needed is 375 g, which corresponds to option B.