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NEET 2025
Exam
NEET
Year
2025
Subject
Chemistry
Chapter
Ionic Equilibrium

NEET 2025 · Chemistry · Ionic Equilibrium

Phosphoric acid ionizes in three steps with their ionization...

Phosphoric acid ionizes in three steps with their ionization constant values Ka1, Ka2\mathrm{K}_{\mathrm{a}_1}, \mathrm{~K}_{\mathrm{a}_2} and Ka3\mathrm{K}_{\mathrm{a}_3}, respectively, While K is the overall ionization constant. Which of the following statements are true? A. log⁡K=log⁡Ka1+log⁡Ka2+log⁡Ka3\log \mathrm{K}=\log \mathrm{K}_{\mathrm{a}_1}+\log \mathrm{K}_{\mathrm{a}_2}+\log \mathrm{K}_{\mathrm{a}_3} B. H3PO4\mathrm{H}_3 \mathrm{PO}_4 is a stronger acid than H2PO4−\mathrm{H}_2 \mathrm{PO}_4^{-}and HPO42−\mathrm{HPO}_4^{2-} C. Ka1>Ka2>Ka3K_{a_1}\gt K_{a_2}\gt K_{a_3} D. Ka1=Ka3+Ka22\mathrm{K}_{\mathrm{a}_1}=\frac{\mathrm{K}_{\mathrm{a}_3}+\mathrm{K}_{\mathrm{a}_2}}{2} Choose the correct answer from the options given below:Phosphoric acid ionizes in three steps with their ionization constant values K_ a_1 , ~K_ a_2 and K_ a_3 ,

Options

  1. AAA and BB only
  2. BAA and CC only
  3. CB,C and D\mathrm{B}, \mathrm{C} \text{ and } \mathrm{D} only \text{ only }
  4. D A, B and C only \text{ A, B and C only }

Correct answer

D.  A, B and C only \text{ A, B and C only }

Step-by-step solution

Phosphoric acid ionizes in three steps with their ionization constant values K_ a_1 , ~K_ a_2 and K_ a_3 ,
For polybasic acid, order of ionization constant is Ka1>Ka2>Ka3\mathrm{Ka}_1\gt\mathrm{Ka}_2\gt\mathrm{Ka}_3 because as negative charge increases, tendency to loose H+\mathrm{H}^{+}ions decreases. Overall K=Ka1×Ka2×Ka3\mathrm{K}=\mathrm{Ka}_1 \times \mathrm{Ka}_2 \times \mathrm{Ka}_3 Taking log on both sides log⁡K=log⁡Ka1+log⁡Ka2+log⁡Ka3\log \mathrm{K}=\log \mathrm{Ka}_1+\log \mathrm{Ka}_2+\log \mathrm{Ka}_3
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