Question:

In which of the following arrangements, the sequence is not strictly according to the property written against it?

HF<HCl<HBr<HI: increasing acid strength

CO2>SiO2<SnO2<PbO2: increasing oxidizing power

B<C<O<N: increasing first ionization enthalpy

NH3<PH3<AsH3<SbH3: increasing basic strength

Solution:

In group 15 hydrides, the basic character decreases on going down the group due to decrease in the availability of the lone pair of electrons because of the increase in the size of elements from N to Bi. Hence, the decreasing order of the basic strength of hydrides is as follows : NH3>PH3>AsH3>SbH3>BiH3. Therefore, option C is correct.