How can you calculate the pH change when you add a strong acid or base to a buffer? Mathematically?

Use the equation for Ka to solve for the new [H+].



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



if you add acid, add the concentration to [HA] and subtract from [A-]. Ka is constant, so just solve for the new [H=] then calculate pH from:



pH = -log[H+]



That's the general idea, but simplified a bit. Make sure you follow moles to Molar and track the total volume to find the actual change to be applied to the [HA] and [A-].How can you calculate the pH change when you add a strong acid or base to a buffer? Mathematically?
pH = pKa + lg([base]eqm/[acid]eqm)

Hope that helps