Answer
$$Volume = 9 \times 10^{-3} \space L = 9 \space mL$$
Work Step by Step
1. Calculate the $[H_3O^+]$:
$$[H_3O^+] = 10^{-pH} = 10^{-1.8} = 2 \times 10^{-2} \space M$$
2. Since HCl is a strong acid, we can say that $[HCl] = [H_3O^+] = 2 \times 10^{-2} \space M$
3. Molar mass of HCl:
$ HCl $ : ( 35.45 $\times$ 1 )+ ( 1.008 $\times$ 1 )= 36.46 g/mol
4. Find the volume of the concentrated solution:
$$5.00 \space L \times \frac{2 \times 10^{-2} \space mol}{1 \space L} \times \frac{36.46\space g}{1 \space mol} \times \frac{100 \space g \space solution}{36.0 \space g} \times \frac{1 \space mL \space solution}{1.179 \space g \space solution} \times \frac{1 \space L}{1000 \space mL}$$
$$Volume = 9 \times 10^{-3} \space L = 9 \space mL$$
