Question

Select the correct order for the given properties.

• A. $NaF>KF>LiF>RbF>CsF$ , Melting point order
• B. $CuCl>NaCl$ , Covalent charater
• C. $BeS{O}_4<CaS{O}_4<SrS{O}_4<BaS{O}_4$ , Thermal stability order
• D. $LiI>NaI>KI>RbI>CsI$ , Solubility order

Answer 1

Answer: (A), (B), (C)

The correct options are
A $CuCl>NaCl$ , Covalent charater
B $NaF>KF>LiF>RbF>CsF$ , Melting point order
C $BeS{O}_4<CaS{O}_4<SrS{O}_4<BaS{O}_4$ , Thermal stability order

A) The correct order for the decreasing melting points of alkali metal fluorides is $NaF>KF>LiF>RbF>CsF$.
With an increase in the atomic number of the alkali metal, the ionic character of the alkali metal fluoride increases and the melting point decreases.
Thus, option A is correct.
B) Copper (I) chloride is more covalent than $NaCl$. Sodium is highly electropositive metal (much more than copper). This results in higher ionic character for $NaCl$.
Thus, option B is correct.
C) As the atomic number of the alkaline earth metals increases, the thermal stability of the sulphates increases due to an increase in the lattice enthalpy.
Hence, the increasing order for the thermal stability of alkaline earth metal sulphates is $BeS{O}_4<CaS{O}_4<SrS{O}_4<BaS{O}_4$.
Thus, option C is correct.
D) With an increase in the atomic number of the alkali metals, the solubility of alkali metal iodides increases due to a decrease in the lattice energy.
The increasing order of the solubility of the alkali metal iodides is $LiI<NaI<KI<RbI<CsI$.
Hence, the option D is incorrect.