The best indicator for the detection of the end point in the titration of a weak acid and a strong base is:

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:
$[K_b(CH_3COO^{-}) = 10^{-9}, pK_a(HPh) = 9.6, \log 2 = 0.3]$

$50 \ mL$ of $0.1 \ M$ of a weak acid $HA$ is titrated with $0.1 \ M$ of $NaOH$. The ionization constant of $HA$ $(K_a)$ is $1.8 \times 10^{-5}$. Using the given information and from the options shown below,the best indicator for the titration of $HA$ with $NaOH$ is $....$

In an acid-base titration,the rapid change in $pH$ near the equivalence point depends on the indicator used. The $pH$ of the solution is related to the ratio of the concentrations of the conjugate acid $(HIn)$ and base $(In^-)$ forms of the indicator by which equation?

Indicator for the titration of $HCl$ and $Na_2CO_3$ would be

The $pH$ indicators are