Question

Mark the incorrect statement(s):

• A. The bond dissociation enthalpy of $F_2$ is greater than that of $C{l}_2$
• B. The boiling point of $HX$ (where $X$ is a halogen) increases uniformly down the group
• C. The solubility of iodine in water increases greatly in the presence of $I^{-}$ ion
• D. $N_3^{–}$ is a pseudo halide

Answer 1

Answer: (A), (B)

The boiling point of $HX$ (where $X$ is a halogen) increases uniformly down the group

$\left(a\right)$ The bond dissociation enthalpy of $C{l}_2$ is greater than that of $F_2$. This is because, in $F_2$ there are more lone pair-lone pair repulsions due to smaller size of $F_2$ which weakens the bond.

$\left(b\right)$ The boiling point order is $HF>HI>HBr>HCl$
$HF$ has the highest boiling point due to the presence of hydrogen bonding whereas, in the other three there are weak london dispersion forces present which increases with increase in molecular mass. Hence $HI$ has a higher boiling point than $HBr$ which in turn has a higher boiling point than $HCl$.

$\left(c\right)$ Though $I_2$ has less affinity for water, it dissolves in water in the presence of $I^{-}$ to form $I_3^{-}$

$\left(d\right)$ $N_3^{–}$ is a pseudo halide