In alkaline buffer solution containing NH4OH and NH4Cl , if some HCl is added its pH will
Correct answer: B. decrease a little
- A. increase a little
- B. decrease a little
- C. remains constant
- D. change but cannot be predicted
Explanation
In an alkaline buffer solution with NH4OH and NH4Cl, the NH4OH acts as a base, and NH4Cl serves as its conjugate acid. When a small amount of HCl is added, it reacts with the NH4OH, forming NH4Cl and water. This reaction consumes some of the NH4OH, causing a slight decrease in the concentration of hydroxide ions (OH⁻) and, consequently, a decrease in pH. The buffer's capacity to resist pH changes, however, prevents a significant drop in pH.
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About Acids, Bases and Salts
Acid and base behaviour is explained through the Bronsted-Lowry transfer of protons and the Lewis donation or acceptance of electron pairs. The topic includes pH, pOH, ionisation and water equilibrium, plus salt formation and hydrolysis, where a salt solution may become acidic, basic or neutral.
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