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Most Important Selected Qs for JEE AdvancedChemistryIonic Equilibrium

Paragraph: Buffer is a solution whose pH does not change significantly on addition of a small amount of acid or alkali or on dilution. Answer the following questions: Question: The amount of ( NH ₄ )₂ SO ₄ to be added to 500 ml of 0.01 M NH ₄ OH solution (pKa for NH ₄ ⁺ is 9.26 ) prepare a buffer of pH 8.26 is :

Options

  1. A0.05 mole
  2. B0.025 mole
  3. C0.10 mole
  4. D0.005 mole

Correct answer

B. 0.025 mole

Step-by-step solution

aligned & pH = pKa + [ Base ] [ Salt ] & [ Base ]= 0.01 500 500 =0.01 aligned Let 'a' milli moles of ( NH ₄ )₂ SO ₄ [ NH ₄⁺ ]= a 2 500 ; [ Salt ]= [ NH ₄⁺ ] aligned & pH =9.26+ [ 0.01 2 a / 500 ] & 8.26=9.26+ [ 0.01 500 2 a ] & a =25 aligned Moles of ( NH ₄ )₂ SO ₄ added =0.025

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