Question

Which of the following is a basic buffer?

• A. \( \mathrm{NaOH + CH_3COONa} \)
• B. \( \mathrm{NaOH + Na_2SO_4} \)
• C. \( \mathrm{K_2SO_4 + H_2SO_4} \)
• D. \( \mathrm{NH_4OH + NH_4Cl} \)

Hint:

Remember:
Weak base + its salt (with strong acid) → basic buffer
Weak acid + its salt (with strong base) → acidic buffer

Answer 1

The Correct Option is D

To determine which of the given combinations forms a basic buffer, we need to understand what constitutes a basic buffer solution. A basic buffer is a solution that consists of a weak base and its conjugate acid (usually in the form of a salt). The buffer maintains the pH by neutralizing small amounts of added acid. Let's analyze each option: 

1. Option 1: \(\mathrm{NaOH + CH_3COONa}\)
   • \(\mathrm{NaOH}\) is a strong base and \(\mathrm{CH_3COONa}\) is the salt of a weak acid, acetic acid, but this doesn't form a basic buffer.
2. Option 2: \(\mathrm{NaOH + Na_2SO_4}\)
   • Both substances are salts resulting in neutral or basic solutions, but they do not form a buffer system.
3. Option 3: \(\mathrm{K_2SO_4 + H_2SO_4}\)
   • This combination results in an acidic solution, not a basic buffer.
4. Option 4: \(\mathrm{NH_4OH + NH_4Cl}\)
   • This is a classic basic buffer system. \(\mathrm{NH_4OH}\) is a weak base and \(\mathrm{NH_4Cl}\) is the salt of that weak base. They work together to resist changes in pH upon the addition of small amounts of acids or bases.

Thus, the correct answer is: \(\mathrm{NH_4OH + NH_4Cl}\). This combination forms a basic buffer solution.