I don't agree with the supposition that a given metal will react faster with a strong acid than a weak one. I think the supposition is based on the fact that weak acids are not completely ionized; therefore, there are more hydrogen ions in a strong acid (one that ionizes completely). And the sentence, as you have expressed it, may intend to talk about acid strengths (that is one is more concentrated or dilute than the other). If that is the intent, then a metal reacts faster with more concentrated acids generally because they contain more hydrogen ions. But no general rule can be observed for that. For example, concentrated H2SO4 is hardly ionized at all since there is little water to form the hydronium ion. For the second part of your question, the answer is not obvious either because you don't specify how much of one versus the other or the concentrations. Volume for volume, and comparing the same kind of acid (monoprotic or diprotic or triprotic) as well as the same strength, then a neutral solution is present when the volume of one solution equals the volume of the other solution.
The net reaction is between hydronium, H3O+, ions and the metal, producing metal anions and hydrogen gas. A strong acid solution has a higher concentration of hydronium ions that a week acid. The rate is higher when the concentration of any one of the reactants is higher.
For part 1, then why is the reaction rate of a given metal with HCl is faster than with acetic acid?
For part 2. how about 1.0M HCl and 0.5MNaOH? Which one needs more volume to produce a neutral solution?
1. HCl is highly dissociated since it is a strong acid. It produces a high concentration of hydrogen ions, H+(aq) in a water solution which are the same as hydronium ions, H3O+. Acetic acid, HC2H3O2, is made of molecules that do not dissociate. Its concentration of hydrogen (hydronium) ions is low. That is why acetic acid reacts more slowly than HCl with metals.
Why does more hydrogen ion results a faster reaction rate?
I got it. Thanks for both of you :)