Q. In which of the following arrangements, the sequence is not strictly according to the property written against it?
A) $CO_{2} < SiO_{2} < SnO_{2} < PbO_{2}$ : increasing oxidising power
B) $HF < HCl < HBr < HI\$: increasing acid strength
C) $NH_{3} > PH_{3} < AsH_{3} < SbH_{3}$ : increasing basic strength
D) $B < C < O < N$ : increasing first ionisation enthalpy
Explanation
(c)
The correct increasing basic strength:
$SbH_{3} < AsH_{3} < PH_{3} < NH_{3}$
$NH_{3}$is the most basic because of its small size, the electron density of electron pair is concentrated over small region. As the size increases, the electron density gets diffused over a large surface area and hence the ability to donate the electron pair (basicity) decreases.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.