Assertion A: pH of a buffer solution does not change on dilution.
Reason R: On dilution the ratio of concentration of salt and acid (or base) remains unchanged.
a)
A and R are true, R is the correct explanation of A
b)
A and R are true, R is not the correct explanation of A
c)
A is true but R is false
d)
A is false but R is true
Correct answer is option 'A'. Can you explain this answer?

Question

Assertion A: pH of a buffer solution does not change on dilution.
Reason R: On dilution the ratio of concentration of salt and acid (or base) remains unchanged.

a)
A and R are true, R is the correct explanation of A
b)
A and R are true, R is not the correct explanation of A
c)
A is true but R is false
d)
A is false but R is true

Correct answer is option 'A'. Can you explain this answer?

Answer

Assertion A: pH of a buffer solution does not change on dilution.

Reason R: On dilution, the ratio of concentration of salt and acid (or base) remains unchanged.

The correct answer is option 'A' - A and R are true, and R is the correct explanation of A.

Explanation:

Buffer solutions are solutions that resist changes in pH when small amounts of acid or base are added to them. They are composed of a weak acid and its conjugate base (or a weak base and its conjugate acid).

The pH of a solution is a measure of its acidity or alkalinity. It is defined as the negative logarithm (base 10) of the concentration of hydrogen ions (H+) in the solution. pH = -log[H+].

A buffer solution maintains a relatively constant pH because of the presence of the weak acid and its conjugate base (or weak base and its conjugate acid). When a small amount of acid or base is added to the buffer solution, the weak acid/base reacts with it, preventing a significant change in pH.

Now, let's analyze the reason (R) given in the assertion.

On dilution, the ratio of concentration of salt and acid (or base) remains unchanged.

When a buffer solution is diluted, the total volume of the solution increases while the amount of solute (acid and conjugate base or base and conjugate acid) remains constant. As a result, the concentration of the solute decreases.

However, the ratio of the concentration of the weak acid and its conjugate base (or weak base and its conjugate acid) remains unchanged because their amounts are not affected by dilution. This is because the ratio of the weak acid and its conjugate base (or weak base and its conjugate acid) depends on their initial amounts and not on the volume of the solution.

Since the pH of a solution is determined by the ratio of the concentration of hydrogen ions (H+), and the ratio of the weak acid and its conjugate base (or weak base and its conjugate acid) does not change on dilution, the pH of a buffer solution remains constant on dilution.

Therefore, the reason (R) explains why the assertion (A) is true. The pH of a buffer solution does not change on dilution because the ratio of the concentration of salt and acid (or base) remains unchanged.

Answer

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