Question

The Henderson's equation states that

• A. pH = pKa + log \left[\frac{[salt]}{[acid]}\right]
• B. pH = pKa - log \left[\frac{[salt]}{[acid]}\right]
• C. pH = pKa - log \left[\frac{[acid]}{[salt]}\right]
• D. pH = pKa + log \left[\frac{[acid]}{[salt]}\right]

Hint:

The Henderson-Hasselbalch equation is a useful tool for calculating the pH of buffer solutions based on the pKa of the acid and the ratio of concentrations of the conjugate base (salt) and the acid.

Answer 1

The Correct Option is A

Step 1: Understanding the Henderson-Hasselbalch equation.
The Henderson-Hasselbalch equation is used to calculate the pH of a buffer solution. It relates the pH of the solution to the pKa of the acid and the ratio of the concentrations of the salt (conjugate base) and acid.
Step 2: Analyzing the options.

• (A) pH = pKa + log \left[\frac{[salt]{[acid]}\right]:} Correct. This is the correct form of the Henderson-Hasselbalch equation, where the pH is related to the ratio of salt and acid concentrations.
• (B) pH = pKa - log \left[\frac{[salt]{[acid]}\right]:} Incorrect. This equation has the wrong sign in front of the logarithmic term.
• (C) pH = pKa - log \left[\frac{[acid]{[salt]}\right]:} Incorrect. This equation has the wrong ratio for the salt and acid.
• (D) pH = pKa + log \left[\frac{[acid]{[salt]}\right]:} Incorrect. This equation has the wrong ratio for the acid and salt.

Step 3: Conclusion.
The correct form of the Henderson-Hasselbalch equation is option (A), where pH is related to the ratio of salt to acid. Final Answer:} pH = pKa + log \left[\frac{[salt]}{[acid]}\right].