[xshadow]

HI All!!!

Today i've studied the buffer solution but i have some doubts looking this graph:


Before, i thought that a buffer solution was a  weak acid/conjugate weak base solution...

But seeing this graph i can see that the Buffer capacity is also good at pH<2 (or on pH>10).
But usually only a strong acid can give a pH value of 2 or less....SO

1) a strong acid solution could be a "buffer solution???
2)if it can, WHY ??!! 

Because when i add some strong base (NaOH) to the solution of HCl there is  the neutralization reaction(H+ +OH-  ---> H2O)  and the concentretion of hydrogen ion decrease quickly...so the pH change!!!

I don't understand this fact...
Someone can explain it??

Thanks a lot.

[Borek]

when i add some strong base (NaOH) to the solution of HCl there is  the neutralization reaction(H+ +OH-  ---> H2O)  and the concentretion of hydrogen ion decrease quickly

It does change, but it is not a quick change.

Add 0.001 moles of HCl to 1L of pure water - what is a pH change? (calculate it!)

Add 0.001 moles of HCl to 1L of 1M NaOH - what is a pH change? Does it qualify as "quick"?