Question

Arrange the following hydrides in the decreasing order of their basicities:
$NH _{3}, AsH _{3}, SbH _{3}, BiH _{3}$ and $PH _{3}$

• A. $NH _{3}> AsH _{3}> SbH _{3}> BiH _{3}> PH _{3}$
• B. $NH _{3}> PH _{3}> AsH _{3}> SbH _{3} \geq BiH _{3}$
• C. $BiH _{3}> SbH _{3}> AsH _{3}> PH _{3} \geq NH _{3}$
• D. $PH _{3}> BiH _{3}> SbH _{3}> AsH _{3}> NH _{3}$

Answer 1

Answer: (B)

The decreasing order of the basicities is
$NH _{3}> PH _{3}> AsH _{3}> SbH _{3} \geq BiH _{3}$
This is because tendency to give lone pair decreases as the size of element of group- $15$ increases.