[mana]

hi all
I have seen this text in silberberg general chemistry book:

 " The closer  [HA]/[A^-] is to 1, the more effective the buffer, If the concentration of one component is more than 10 times the concentration of the other, buffering action is poor. Since log10 = 1, buffers have a usable range within ± 1 pH unit of the pKa of the acid component."

I can't understand why the [HA]/[A^-] should be near 1 and also how we get that when the concentration of one component>10 so the other component concentration should be poor?

[AWK]

https://www.chembuddy.com/?left=pH-calculation&right=pH-buffer-capacity

[Babcock_Hall]

It might also help to look at the slope of the titration curve near the pK_a.  What does having a small slope vs. a large slope mean from the perspective of buffering action?