Q9 / 125 · BITSAT 2015 · Chemistry

What is the correct increasing order of Bronsted bases?

  • Correct answer
    A
    $\mathrm{ClO}_{4}^{-}<\mathrm{ClO}_{3}^{-}<\mathrm{ClO}_{2}^{-}<\mathrm{ClO}^{-}$
  • B
    $\mathrm{ClO}_{4}^{-}>\mathrm{ClO}_{3}^{-}>\mathrm{ClO}_{2}^{-}>\mathrm{ClO}^{-}$
  • C
    $\mathrm{ClO}_{3}^{-}<\mathrm{ClO}_{4}^{-}<\mathrm{ClO}_{2}^{-}<\mathrm{ClO}^{-}$
  • D
    $\mathrm{ClO}^{-}>\mathrm{ClO}_{3}^{-}>\mathrm{ClO}_{2}^{-}<\mathrm{ClO}_{4}^{-}$

Solution

$\mathrm{ClO}_{4}^{-}<\mathrm{ClO}_{3}^{-}<\mathrm{ClO}_{2}^{-}<\mathrm{ClO}^{-}$ is the correct increasing order of Bronsted base. With increase in the number of oxygen atoms in the conjugate bases, the delocalisation of the $\pi$ bond becomes more and more extended. This results in decrease in the electron density. Consequently basicity also decreases.

Hence, the correct answer is option: 'A'.

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