Question

At the end point, there is a sharp change of colour in the indicator. This happens because the

• A. $pH$ a end point changes sharply
• B. Structure of the indicator changes
• C. Colour of indicator is adsorbed by water
• D. Dissociation constant of acids and base differ by 10

Answer 1

Answer: (A), (B)

a. Correct: At the point, $\left[H^{\oplus }\right]$ becomes small and to change it, small amount of $[\stackrel{\ominus }{O}H]$ is required. When $\left[H^{\oplus }\right]$ change from $10^{-6}M$ to $10^{-7}M,pH$ change is one, but the volume of $NaOH$ required for this change is very small. So, the curve changes sharply
b. Correct: Quinoid structure is obtained
(c) and (d) are wrong statements