$50 \ mL$ 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 $....$

  • A
    Methyl orange (changes colour from red to yellow as the $pH$ changes from $3.2$ to $4.4$)
  • B
    Methyl red (changes colour from red to yellow as the $pH$ changes from $4$ to $6.3$)
  • C
    Phenolphthalein (changes from colourless to pink as the $pH$ changes from $8.3$ to $11$)
  • D
    Sodium salt of Alizarin yellow (changes colour from yellow to red as the $pH$ changes from $10$ to $12$)

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Similar Questions

Phenolphthalein is a suitable indicator for the titration of:

At what $pH$ will an indicator with $K_b = 1 \times 10^{-11}$ show a color change in a $1 \times 10^{-4} \ M$ solution?

The rapid change of $pH$ near the stoichiometric point of an acid-base titration is the basis of indicator detection. 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 the expression:

The pink colour of phenolphthalein in an alkaline medium is:

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.

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