* HCl is a strong acid. Strong acids completely ionize in solution, meaning they donate all their hydrogen ions (H+).

* Concentration refers to the amount of solute in a solution. 5M HCl means there are 5 moles of HCl dissolved in 1 liter of solution. This is a high concentration, indicating a large amount of acid is present.

Therefore, 5M HCl is a concentrated strong acid.