What is the [H+] of the 0.25 M HCl solution?
I'm not given a Ka value, so I'm assuming I won't need one to solve this particular problem?
To determine the [H+] concentration of a solution, you can use the concept of strong acids. Strong acids completely dissociate in water, meaning that they ionize 100% into their constituent ions. HCl is a strong acid, so it dissociates completely into H+ (hydrogen ions) and Cl^- (chloride ions) in water.
In a 0.25 M HCl solution, the concentration of HCl is given as 0.25 M. Since HCl dissociates completely, the concentration of H+ ions is also 0.25 M. Therefore, the [H+] of the 0.25 M HCl solution is also 0.25 M.
No Ka value is required in this case because strong acids completely dissociate, and the concentration of H+ ions is equal to the concentration of the acid itself.