Answer
I would dilute 4.216ml of the 12M HCl solution, with sufficient water to reach 1600ml of solution.
Work Step by Step
1. Calculate the $[H_3O^+]$ necessary to reach pH = 1.50
$[H_3O^+] = 10^{-pH}$
$[H_3O^+] = 10^{- 1.5}$
$[H_3O^+] = 3.162 \times 10^{- 2}M$
2. Since $HCl$ is a strong acid: $[HCl] = [H_3O^+] = 3.162 \times 10^{- 2}M$
3. Use the dilution equation to find the necessary volume of the 12M HCl solution:
$C_1 * V_1(L) = C_2 * V_2(L)$
$ 0.03162* 1.6= 12 * V_2$
$ 0.050592 = 12 * V_2$
$V_2 = 0.004216L = 4.216ml$
