Question

The effectiveness of a buffer is measured in terms of:
1. Buffer Action
2. Buffer Capacity
3. pKa
4. None of these

Answer 1

Correct Answer - Option 2 : Buffer Capacity

Explanation:

• A good buffer solution must contain appreciable amounts of both a weak acid and its salt or a weak base and its salt so that they are able to modify the effect of an acid or base added to them.
• This is the origin of the term buffer.
• The larger the amount, the greater is the buffering capacity, that is, the effectiveness of a buffer solution to resist a change in pH.
• Buffer capacity may be defined as the number of moles of the acid or base required which when added to one litre of a buffer solution, change the pH by one unit.
• The condition for maximum buffer capacity is that the ratio of [Salt]/[Acid] for an acidic buffer or [Base][Salt] of a basic buffer should be unity.
• A buffer solution generally loses its usefulness when one component of the buffer pair is less than about one tenth of the other.
• Weak acids and their salts are better as buffers when their pH < 7.
• Weak bases and their salts are better buffers when their pH > 7.

Hence, the effectiveness of a buffer is measured in terms of Buffer Capacity.

• Buffer Action is the mode of action of buffer to neutralize the effects of addition of acids and bases to them.
• pKa of acid is the negative logarithm of the dissociation.