Answer:
Here's what I get
Step-by-step explanation:
In the figure below, assume the black dots are H⁺ ions and the open circles are Cl⁻ ions.
Also, assume that the square for 0.10 mol·L⁻¹ HCl contains four dots and four circles.
Then, the square for 0.20 mol·L⁻¹ HCl will contain eight dots and eight circles.