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JEE MainChemistryp Block Elements (Group 15, 16, 17 & 18)

For the hydrides of Group 15 elements ( EH ₃ ), it is observed that the E-H bond dissociation enthalpy decreases significantly from NH ₃ to BiH ₃ . Which of the following pairs of property trends is primarily and directly explained by this decrease in bond enthalpy down the group?

Options

  1. AThe decrease in Lewis basicity and the decrease in thermal stability
  2. BThe increase in boiling point and the increase in reducing character
  3. CThe decrease in H-E-H bond angle and the decrease in Lewis basicity
  4. DThe decrease in thermal stability and the increase in reducing character

Correct answer

D. The decrease in thermal stability and the increase in reducing character

Step-by-step solution

The E-H bond dissociation enthalpy decreases down Group 15 due to the increasing size of the central atom E , which leads to less effective orbital overlap with the small 1s orbital of hydrogen. 1. Thermal stability depends directly on the strength of the E-H bond. As the bond dissociation enthalpy decreases, less energy is required to break the bond, causing thermal stability to decrease from NH ₃ to BiH ₃ . 2. Reducing character depends on the ease with which the hydride can release hydrogen. A lower E-H bond dis

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