Q65 / 180 · AIIMS 2014 · Chemistry

Which is correct regarding acidity?

  • Correct answer
    A
    $\mathrm{H}_2 \mathrm{~S} < \mathrm{H}_2 \mathrm{Se}$
  • B
    $\mathrm{H}_2 \mathrm{~S}>\mathrm{H}_2 \mathrm{Se}$
  • C
    $\mathrm{H}_2 \mathrm{Se}>\mathrm{H}_2 \mathrm{Te}$
  • D
    None of these.

Solution

Due to decrease in bond $(\mathrm{H}-E$, where $E=\mathrm{O}, \mathrm{S}, \mathrm{Se}, \mathrm{Te}$ ) dissociation enthalpy down the group, acidic character increases. Hence, the order is : $\mathrm{H}_2 \mathrm{O} < \mathrm{H}_2 \mathrm{~S} < \mathrm{H}_2 \mathrm{Se} < \mathrm{H}_2 \mathrm{Te}$

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

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