The titration curve of weak acid vs. strong base with phenolphthalein as indictor) is shown below.
The Kphenolphthalein = 4 × 10–10.
Select the correct option:
A
It can be used as an indicator for the titration of weak acid with weak base.
B
It begins to change colour at pH = 8.4 C.
C
It is a weak organic base D.
D
It is colourless in acidic medium
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
Sol. (B) pkın $=-\log \left(4 \times 10^{-10}\right)=9.4$
Indicator range $\Rightarrow \mathrm{pk} \ln \pm 1$
i.e., 8.4 to 10.4
(D) In acidic medium, phenolphthalein is in unionized form and is colourless.
Hello 👋 Welcome to Competishun – India’s most trusted platform for JEE & NEET preparation. Need help with JEE / NEET courses, fees, batches, test series or free study material? Chat with us now 👇
