Answer:

Step-by-step explanation:
The volume of the stock solution required can be found by using the formula:

where
C1 is the concentration of the stock solution
V1 is the volume of the stock solution
C2 is the concentration of the final solution
V2 is the volume of the final solution
From the question:
C1 = 10 M
V1 = ?
C2 = 0.5 M
V2 = 0.45 L
Making V1 the subject we have;


We have the final answer as:
0.023 L