If a very small amount of $HPh$ (phenolphthalein) is added to a $0.1 \ M$ aqueous solution of $CH_3COONa$,the fraction of the indicator that exists in the colourless form is:
$[K_b(CH_3COO^{-}) = 10^{-9}, pK_a(HPh) = 9.6, \log 2 = 0.3]$

For an acid indicator with $K_{in} = 1.0 \times 10^{-5}$, the color change occurs when the concentration of the indicator is $1 \times 10^{-3} \ M$. Find the $pH$ at which the color change occurs.

The titration curve of a weak acid vs. a strong base with phenolphthalein as an indicator is shown below. The $K_{In} = 4 \times 10^{-10}$. Given: $\log 2 = 0.3$. The number of the following statements which is/are correct about phenolphthalein is $.....$.
$A$. It can be used as an indicator for the titration of a weak acid with a weak base.
$B$. It begins to change colour at $pH = 8.4$.
$C$. It is a weak organic base.
$D$. It is colourless in an acidic medium.

Phenolphthalein is not a good indicator for titrating:

The $pH$ indicators are

Which indicator works in the $pH$ range of $8 - 9.8$?