Final answer:
A buffer is a solution made of a weak acid and its conjugate base that can resist changes in pH when small amounts of acid or base are added. When a strong acid is added, the weak acid in the buffer reacts with the acid, forming its conjugate base and preventing a significant decrease in pH. The moles of weak acid and conjugate base in the solution can be calculated using the Henderson-Hasselbalch equation.
Step-by-step explanation:
A buffer is a solution that can resist changes in pH when small amounts of acid or base are added to it. It is made up of a weak acid and its conjugate base. One example of a buffer is a solution made of acetic acid (the weak acid) and sodium acetate (the salt).
When a strong acid, such as HCl, is added to the buffer solution, the weak acid in the buffer reacts with the acid, forming its conjugate base. This reaction helps to neutralize the additional hydrogen ions and prevents a significant decrease in pH. As a result, the buffer solution resists the addition of the HCl.
To calculate the moles of weak acid and conjugate base in the solution before and after the addition of HCl, you can use the Henderson-Hasselbalch equation, which relates the pH of a buffer to the concentrations of the weak acid and its conjugate base.