To calculate the change in pH when a strong acid is added to a buffer solution containing a weak acid and its conjugate base, we can use the Henderson-Hasselbalch equation:pH = pKa + log [A-]/[HA] where pH is the pH of the solution, pKa is the negative logarithm of the acid dissociation constant Ka of the weak acid, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid.First, we need to know the initial concentrations of the weak acid and its conjugate base, as well as the amount of strong acid added to the solution. Let's assume the following:Initial concentration of weak acid HA : 0.1 MInitial concentration of conjugate base A- : 0.1 MKa of the weak acid: 1.0 x 10^-5Volume of the buffer solution: 1 LAmount of strong acid added: 0.01 molesWhen the strong acid is added to the buffer solution, it will react with the conjugate base A- to form more weak acid HA and water. The reaction can be represented as:H+ + A- HASince 0.01 moles of strong acid are added, 0.01 moles of A- will react to form 0.01 moles of HA. The new concentrations of HA and A- can be calculated as follows:New concentration of HA: 0.1 + 0.01 M = 0.11 MNew concentration of A-: 0.1 - 0.01 M = 0.09 MNow we can use the Henderson-Hasselbalch equation to calculate the new pH of the solution:pH = pKa + log [A-]/[HA] pH = -log 1.0 x 10^-5 + log 0.09/0.11 pH 4.74To find the change in pH, we need to compare the new pH with the initial pH of the buffer solution. The initial pH can be calculated using the Henderson-Hasselbalch equation with the initial concentrations:Initial pH = -log 1.0 x 10^-5 + log 0.1/0.1 Initial pH 4.74 since log 1 = 0 Since the initial pH and the new pH are approximately the same, the change in pH is very small close to 0 . This demonstrates the buffering capacity of the solution, as it is able to resist changes in pH when a strong acid is added.