Question

How many of the following trends is(are) CORRECT with respect to the properties of hydrides of group $15$ elements?
i. Basic strength:
$NH _{3}> PH _{3}> AsH _{3}> SbH _{3} \geq BiH _{3}$
ii. Reducing character:
$NH _{3}< PH _{3}< AsH _{3}< SbH _{3}< BiH _{3}$
iii. Thermal stability:
$NH _{3}> PH _{3}> AsH _{3}> SbH _{3}> BiH _{3}$
iv. Boiling point:
$NH _{3}< PH _{3}< AsH _{3}< SbH _{3}< BiH _{3}$

Answer 1

The boiling point of $NH _{3}$ is higher than that of $PH _{3}$ and $AsH _{3}$. This is due to its tendency to form hydrogen bonds. Hence, the trend in boiling point is
$PH _{3}< AsH _{3}< NH _{3}< SbH _{3}< BiH _{3}$.