CHEMISTRY COMMUNITY

Can someone explain to me a section of the notes? It was when he asked "Q2: A biological acid, HA, has pKa = 4.22. What's the Ka value of the acid?" I don't understand the part after that says "Is the acid neutral or negatively charged at pH 6?" and the little section under it. Thank you!

Tiffany Chao 3K wrote:Can someone explain to me a section of the notes? It was when he asked "Q2: A biological acid, HA, has pKa = 4.22. What's the Ka value of the acid?" I don't understand the part after that says "Is the acid neutral or negatively charged at pH 6?" and the little section under it. Thank you!

So, the lecture notes says "under acidic conditions (pH<pKa), the acid is protonated as HA"

The question gives us that the acid is pH=6. The pKa is also given to us and it is pKa=4.22. Since 4.22<6, the solution is more acidic and more protonated (positive charge)

The pKA as to be either lower (more acidic) than pH6, or higher (more basic) than pH6. Since 4.22 is less than 6, it is more acidic, meaning it is more positive.