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    "When the student prepares the buffer solution, the volume of the solution increases slightly.
    Suggest whether the pH of the buffer solution would be the same, greater than, or less than your calculated value in c) i).
    Explain your reasoning."

    Context: buffer solution is made from CH3COOH (the original solution) and CH3COONa (dissolved solid) with a calculated pH of 4.5

    The answer is that it stays the same, but I don't understand why or how. Any help would be greatly appreciated!

    (btw this is from the jun 2017 paper 1)

    Ka = [H+] x ([A-]/[HA])

    [A-] is decreased on increase in volume, but [HA] decreases by the same amount, the ratio of [A-] to [HA] doesn't change and hence [H+] also doesn't change.
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