# What is the meaning of the term 'reserve acidity'?

In $\ce{CH3COOH/CH3COONa}$ buffer, the reserve acidity of the solution is due to the $\ce{CH3COO-}$ ions.

What is the meaning of the term of 'reserve acidity' in the above statement?

• One would expect buffers to maintain constant pH. Thus, in that context, reserve acidity of CH3COO- ions could mean that the CH3COO- ions help neutralize the base that has been added to the buffer solution. Though, I've been reading the mech here, and apparently my intuition doesn't seem to be correct. Will wait for someone to post a proper answer. – Gaurang Tandon Feb 17 '18 at 2:57

In your question, the $\ce{CH3COO-}$ is able to react with any Hydrogen ions that are added to the solution, decreasing the $[\ce{CH3COO-}]$ while increasing the $[\ce{CH3COOH}]$. It takes care of any excess acidity, hence, it is called as the reserve acidity. Similarly, the $\ce{CH3COOH}$ should be called the reserve basicity, as it can reach with any base to prevent much pH change.