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JEE Main 2007
Exam
JEE Main
Year
2007
Subject
Chemistry
Chapter
Ionic Equilibrium

JEE Main 2007 · Chemistry · Ionic Equilibrium

The pKa of a weak acid (HA) is 4.5 . The pOH of an aqueous buffered...

The pKa\mathrm{pKa} of a weak acid (HA)(\mathrm{HA}) is 4.54.5. The pOH\mathrm{pOH} of an aqueous buffered solution of HA\mathrm{HA} in which 50%50 \% of the acid is ionized is

Options

  1. A4.54.5
  2. B2.52.5
  3. C9.59.5
  4. D7.07.0

Correct answer

C. 9.59.5

Step-by-step solution

For buffer solution pH=pKa+log⁡[ Salt ][ Acid ]=4.5+log⁡[ Salt ][ Acid ]\begin{aligned} & \mathrm{pH}=\mathrm{pK}_{\mathrm{a}}+\log \frac{[\text{ Salt }]}{[\text{ Acid }]} \\ & =4.5+\log \frac{[\text{ Salt }]}{[\text{ Acid }]} \end{aligned} as HA\mathrm{HA} is 50%50 \% ionized so [Salt]=[Acid][\text{Salt}]=[\text{Acid}]pH=4.5pH+pOH=14⇒pOH=14−4.5=9.5\begin{aligned} & \mathrm{pH}=4.5 \\ & \mathrm{pH}+\mathrm{pOH}=14 \\ & \Rightarrow \mathrm{pOH}=14-4.5=9.5 \end{aligned}$$ Hence (C) is correct.
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