Acids in solution

[kristinalaudis3e]

Hello,

In lecture Lavelle stated that acid in a solution will be at pH 6. Does he mean the acid itself is at pH 6 or does he mean the solution will become pH 6?

[705383815]

pH refers to the concentration of H+ in a solution.

[Andreas Krumbein 1L]

The solution is at pH 6, since the way in which pH is measured is through the H₃O⁺ concentration, which requires that the water molecules ionize the H⁺ from the rest of the acid's molecular complex. Without being in solution, the H⁺ remains attached to the rest of the acid and no H₃O⁺ can be measured.

[Izamary Marquez 2H]

Also, I am a little confused on how we know whether it's 100% associated... Can we determine this based on the Lewis Structure of the molecule? In general, what does it mean for the acid to be "completely associated"?

[AJackman]

The solution pH changes. Presumably if the acid is added to the solution it's all the solution and therefore all the same pH, however, so I don't think it matters.

[Arjun_Anumula_3E]

Whenever pH or acidity is mentioned, it always means that there is an accompanying solution. Without water or solution, these acids would be normal molecules that are not actively donating protons. It is only until acid comes into contact with water (such as pouring HCl onto your skin) causes the tissues and water in them to accept protons rapidly, lowering the pH and damaging the region (acid burns)