Go though worked example, step by step (maths not hard if its broken down into small steps). Calculate the pH of a buffer solution, given the amounts. Break down into small steps using images of board or notepad and click and reveal. (saving the video/animation showing teaching teachniques for the DU section).

Show that the reverse calculation can be done, eg given the pH of the buffer required, calculate the quantites required (ratio). Buffer can be made up using any concentrations of acid and salt in that ratio.

Ka = [H+][A-]/[HA]

Approx pH of acid buffer solution can be calc from composition and acid dissociation constant

pH = pKa - log10 [acid]/[salt]

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