5.1.3 acids bases and buffers

Question 1

in a buffer solution of methanoic acid and sodium methanoate, why does dilution not cause a change in pH

Answer 1

[HA] and {A-] both decrease proportionally so the ratio between them stays the same, Ka stays the same and
[H+] = Ka * [HA]/[A-]
so [H+] constant therefore pH constant.