Answer:

Step-by-step explanation:
Hello!
In this case, in a dilution process, water is added to a solute in order to decrease its concentration but increase the volume of the solution. It means that if we have 20.0 mL of a 12.0-M solution of HCl and we want a 0.500-M solution, we need to apply the following formula considering that the moles remain unchanged:

Thus, solving for the final volume is:

So plugging in the values we obtain:

Now, since the initial volume of acid was 20.0 mL and the final volume is 480 mL, the added volume of distilled water is:

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