Strange Buffer Question - any ideas?

Hi,

I need to compare the following buffer solutions:
- 25cm3 of 0.1moldm-3 ethanoic acid and 25cm3 of 0.1moldm-3 sodium ethanoate (equimolar concentrations).
- 25cm3 of 0.01moldm-3 ethanoic acid and 25cm3 of 0.1moldm-3 sodium ethanoate (NOT equimolar concentrations).

The pH of the equimolar buffer was 4.48, the pH of the non-equimolar buffer was 5.63.

When 1cm3 or 1moldm-3 HCl was added to both buffers, the equimolar buffer pH changed to 4.47. In the non-equimolar buffer, the pH changed more significantly to 5.45.

I need to explain the chemistry behind why the non-equimolar buffer was less effective (in terms of how the position of equilibrium changed etc.)

Any ideas?

I agree with this "With the second scenario there is much more A- than HA and the pH shifts to a greater extent." but surely if HA is limited and A- is in excess, then adding HCl would actually sort of counter the lack of HA? Why is the system less able to respond than an equimolar?