Question

Chemistry question over buffers?

Answer 1

Recall the buffer equation...

Explanation:

And this holds that `pH=pK_a+log_10{[[A^-]]/[[HA]]}`

So ideally we want an acid and conjugate base whose `pK_a` is moderately close to the desired `pH`.

We want `pH=5.50`...i.e. `[H_3O^+]=10^(-5.50)=3.16xx10^-6*mol*L^-1`...so `"acid 3"` is probably the safest bet.