Question

What volume of concentrated hydrochloric acid (12.0 M HCl) is required to make 2.0 liters of a 3.0 M HCl solution?

Answer 1

If you have 12 M HCl \(\sf \color{red}{M_1}\)
and you want a concentration of \(\sf \color{red}{M_2}\)
and a total volume of 2.0 L \(\sf \color{blue}{V_2}\)

Then simply use the dilution equation: \(\sf \color{red}{M_1}\)V\(_1\) = \(\sf \color{red}{M_2}\)\(\sf \color{blue}{V_2}\)

rearrange using algebra to solve for the initial volume.
That means that you're using V\(_1\) liters of HCl and diluting the rest with water to make a total of 2.0 L.

Does that make sense?

Answer 2

This is not qualitative, and hence, your concentration is simply approximate.