A buffer contains 0.10 mol of acetic acid and 0.13 mol of sodium acetate in 1.00 L. (c) What is the pH of the buffer after the addition of 0.02 mol of HNO3?

Verified step by step guidance

1. Identify the components of the buffer system: acetic acid (CH3COOH) and sodium acetate (CH3COONa).
2. Recognize that the addition of HNO3, a strong acid, will react with the acetate ion (CH3COO^-), the conjugate base in the buffer.
3. Calculate the moles of acetate ion (CH3COO^-) that will react with the added HNO3. Since 0.02 mol of HNO3 is added, it will react with 0.02 mol of CH3COO^-.
4. Subtract the moles of CH3COO^- that reacted from the initial moles of CH3COO^- to find the new concentration of CH3COO^- in the buffer.
5. Use the Henderson-Hasselbalch equation, \( \text{pH} = \text{pK}_a + \log \left( \frac{[\text{CH}_3\text{COO}^-]}{[\text{CH}_3\text{COOH}]} \right) \), to calculate the new pH of the buffer, using the updated concentrations of CH3COOH and CH3COO^- after the reaction.

Key Concepts

Buffer Solutions

A buffer solution is a system that resists changes in pH upon the addition of small amounts of acid or base. It typically consists of a weak acid and its conjugate base, or a weak base and its conjugate acid. In this case, acetic acid (a weak acid) and sodium acetate (its conjugate base) form a buffer that can maintain pH stability when acids or bases are introduced.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of a buffer solution. It is expressed as pH = pKa + log([A-]/[HA]), where pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the weak acid. This equation helps in determining the pH after the addition of acids or bases to the buffer.

Acid-Base Neutralization

When an acid is added to a buffer solution, it reacts with the conjugate base present in the buffer, leading to a decrease in the concentration of the base and an increase in the concentration of the acid. This neutralization process is crucial for understanding how the pH of the buffer changes upon the addition of strong acids, such as HNO3 in this scenario, and is essential for calculating the new pH.