Make 300 mL of a 0.4M NaOH solution.

Done. That was easy.

o 6.025 ml

To make a 0.4M NaOH solution, you need to know the molarity and volume of the stock solution of NaOH that you have. Assuming you have a stock solution of NaOH with a higher concentration, you can use the formula:

C1V1 = C2V2

Where:
C1 is the initial concentration of the stock solution (unknown)
V1 is the initial volume of the stock solution (unknown)
C2 is the desired concentration of the final solution (0.4M)
V2 is the final volume of the solution you want to prepare (300 mL)

Let's rearrange the formula and solve for the initial volume of the stock solution (V1):

V1 = (C2 * V2) / C1

Now, substitute the known values into the formula. Let's assume you have a 2M NaOH stock solution:

V1 = (0.4M * 300 mL) / 2M
V1 = (0.4 * 300) / 2
V1 = 120 / 2
V1 = 60 mL

So, you need 60 mL of a 2M NaOH stock solution and you can dilute it to 300 mL to make a 0.4M NaOH solution.