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Calcium lactate is a salt of weak acid i.e., lactic acid having general formula C a ( L a C ) 2 . Aqueous solution of salt has 0.3 M concentration. pOH of solution is 5.60. If 90% of the salt is dissociated then what will be the value of p K a ?

Options

  1. A2.8 – log (0.54)
  2. B2.8 + log (0.54)
  3. C2.8 + log (0.27)
  4. DNone of these

Correct answer

A. 2.8 – log (0.54)

Step-by-step solution

C a ( L a C ) 2 → C a 2 + + 2 L a C - Concentration of salt = 0.6 2 = 0.3 M Concentration of L a C - after dissociation = 2 × 0.3 × 0.9 = 0.54 M pH after salt hydrolysis may be calculated as, pH   =   1 2 [(pK w   +   pK a   +   log(LaC − )] 14 - 5.6 = 1 2 [ 14 + p K a + log ⁡ 0 . 54 ] p K a = 2.8 - log ⁡ 0 . 54

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