1 Explain the differences observed when you added drops of a

1. Explain the differences observed when you added drops of acid or base to the water versus when the drops were added to the phosphate buffer.

Solution

Ans. When a drop of acid or base is added to water (distilled water, pH = 7.0), a change in pH is noted. When the same is added to phosphate buffer, say at pH 7.4, no change in pH is noted.

            I. Water (pH 7.0) + acid -------> pH lowers below 7.0, say new pH is 6.0.

            II. Water (pH 7.0) + base -------> pH rises above 7.0, say new pH is 8.0.

            III. Phosphate buffer (pH 7.4) + acid or base -------> NO change in pH.

Since, phosphate buffer resists pH change after addition of small quantity of acid/base. Therefore, no change in pH is noted after small amount of acid/alkali is added to it.