Is total acidity of a solution equal to actual acidity(pH)? Or is total acidity equal to the [H+]?

Question

the total acidity is what u can find after titrating a solution. Now, this anwer is in moles/litre (M). I understand that [H+] is also in M. If [H+] is found then the actual acidity (pH, which is found using the pH meter) should be the same thing as the pH calculated using the [H+], rite? Now, is total acidity equal to the actual acidity or is it equal to the [H+]? Pls respond as soon as possible.

Answer 1

I am not sure I understand your question and definitions.

pH=-log[H+] or more correctly you would measure with a pH-meter
pH=-log{H+} where {H+} is the activity of H+ and it is {H+}= γ[H+]
where γ depends on the ionic strength (for very dilure solutions γ is approximately 1 and activity= concentration)

If we are talking about strong acids, then the total acidity as you call it will be equal to the [H+], as the dissociation is 100%.

If we are talking about weak acids then the total acidity is higher than the [H+] you would measure with a pH-meter. Here is why.

Imagine you have a weak monoprotic acid

HA <=> H+ + A-

what you measure with the pH-meter will be the [H+] at the equillibrium, thus there will be some H+ "captured" in the non-dissociated HA molecules that are at equillibrium.

However when you titrate with a base, all H+ will react and thus you are calculating the total concentration of acid which is
[HA]total=[HA]equillibrium+ [H+]equillibrium

Answer 2

You have to be careful with the term acidity. You have to define it for your situation. There is another definition from the wastewater industry that means the amount of base needed to raise the pH of a solution to a new pH (determined by the tester). It is used for measuring buffer capacity. The final pH can be neutral or anything else (8.2 and 4.5 are sometimes used).

What you get from a titration is amount of base needed, the starting aicd concentration, or the pHs. Unless you have defined it, you don't get "acidity".

Answer 3

I'm not actually sure I understand what you are asking, and I was a chem major. Maybe this will help tho? Remember that [H+] is the concentration of H+ ions in solution, so it's Moles/Liter. pH is the negative log of H+ concentration. So, pH= - log [H+]. Does that help?

Answer 4

I don't quite get your question.

pH = -log[H+]

So if you report your answer as pH or as the [H+] it is the same thing stated in different ways?

Are you asking about the nonidealities of the pH meter?

If you can clarify I can try and help..