Final answer:
To find the pH after adding barium hydroxide to hydrocyanic acid, the moles of acid and base need to be calculated, and an ICE table or Henderson-Hasselbalch equation should be applied using the acid's Ka value.
Step-by-step explanation:
The student's question involves the calculation of pH during a titration of weak acid with a strong base. In this scenario, hydrocyanic acid (a weak acid) is being titrated with barium hydroxide (a strong base). To determine the pH of the solution after adding 9.06 mL of the base to the weak acid, the student has to carry out a reaction stoichiometry and equilibrium calculation. Since hydrocyanic acid is a weak acid, it does not dissociate completely in water, which implies that upon addition of the base, a buffer system is formed until the equivalence point is reached. The Henderson-Hasselbalch equation or an ICE table (Initial, Change, Equilibrium) is often used to compute the pH of buffer solutions, considering the amounts of acid and conjugate base in the solution and the acid's dissociation constant (Ka).