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99 Percentile Qs Bank for JEE MainChemistryIonic Equilibrium

In an aqueous solution, the ionization constants for carbonic acid are K 1 = 4.2 × 1 0 - 7 and K 2 = 4.8 × 1 0 - 11 Select the correct statement for a saturated 0.034 M solution of the carbonic acid:

Options

  1. AThe concentration of H + is double that of CO 3 2 - .
  2. BThe concentration of CO 3 2 - is 0.034 M .
  3. CThe concentration of CO 3 2 - is greater than that of HCO 3 - .
  4. DThe concentration of H + and HCO 3 - are approximately equal.

Correct answer

D. The concentration of H + and HCO 3 - are approximately equal.

Step-by-step solution

H 2 CO 3 ⇌ H + + HCO 3 - ; K 1 = 4.2 × 1 0 - 7 HCO 3 - ⇌ H + + CO 3 2 - ; K 2 = 4.8 × 1 0 - 1 1 ∵   K 1 ≫ K 2 , so H 2 CO 3 ionises more than HCO 3 - and hence, contribution of H + is mostly due to ionization of carbonic acid. Thus, the concentrations of H + and HCO 3 - are approximately equal.

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