What is the concentration of h+ ions in a solution of hydrochloric acid that was prepared by diluting 25.0 ml of concentrated (11.6 m ) hcl to a final volume of 500.0 ml?

We can use the following formula to find the concentration of HCl in the diluted solution.
c1v1 = c2v2
c1 is concentration and v1 is volume of concentrated solution
c2 is concentration and v2 is volume of diluted solution
substituting values in the equation,
11.6 M x 25.0 mL = C x 500.0 mL 
C = 0.58 M
The new concentration of HCl is 0.58 M
Since HCl is a strong acid, it completely dissociates into H⁺ ions.
therefore [HCl] = [H⁺]
since [HCl] = 0.58 M
then [H⁺] = 0.58 M