Calculate pH at which an acid indicator HIn with concentration 0.1 M changes its colour ( K a for HIn = 1 × 1 0 - 5 ).

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Question: Answered & Verified by Expert

Calculate pH at which an acid indicator HIn with concentration 0.1 M changes its colour (

K_{a}

for HIn

= 1 \times 1 0^{- 5}

).

ChemistryIonic EquilibriumJEE Main

Solution:

2643 Upvotes Verified Answer

The correct answer is: 5

Indicator equation is

p H = p K_{I n} + \log \frac{[I n^{-}]}{[H I n]}

Colour change takes place when

[I n^{-}] = [H I n]

i.e., when

p H = p K_{I n} = 5

.

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