NEET2012ChemistryIonic EquilibriumActual
Buffer solutions have constant acidity and alkalinity because
Options
- Athese give unionised acid or base on reaction with added acid or alkali
- Bacids and alkalies in these solutions are shielded from attack by other ions
- Cthey have large excess of H ⁺ or OH ⁻ ions
- Dthey have fixed value of pH
Correct answer
A. these give unionised acid or base on reaction with added acid or alkali
Step-by-step solution
If small amount of an acid or alkali is added to a buffer solution, it converts them into unionised acid or base. Thus, its pH remains unaffected or in other words its acidity/alkalinity remains constant. e.g., aligned & H ₃ O ⁺+A⁻ H ₂ O + H A & ⁻ OH + H A H ₂ O +A⁻ aligned If acid is added, it reacts with A⁻ to form undissociated HA. Similarly, if base/alkali is added, OH ⁻ combines with H A to give H ₂ O and A⁻ and thus, maintains the acidity/ alkalinity of buffer solution.