Question

Select the correct order of their thermal stability :

• A. $LiF>NaF>KF>RbF>CsF$
• B. $KF>KCl>KBr>KI$
• C. $LiCl>NaCl>KCl>RbCl>CsCl$
• D. $L{i}_{2}O>N{a}_{2}O>K_{2}O>R{b}_{2}O$

Answer 1

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

The correct options are
A $KF>KCl>KBr>KI$
B $LiF>NaF>KF>RbF>CsF$
C $LiCl>NaCl>KCl>RbCl>CsCl$
D $L{i}_{2}O>N{a}_{2}O>K_{2}O>R{b}_{2}O$

A) On moving down the group, the thermal energy and the lattice energy of the fluorides of alkali metals decrease. The decreasing order is $LiF>NaF>KF>RbF>CsF$.

Hence, the option A is correct.

B) The decreasing order of the thermal stability and the lattice energy of halides of potassium is $KF>KCl>KBr>KI$. On moving down the group, as the atomic number of halogen increases, its thermal stability increases.

Hence, the option B is correct.

C) On moving down the group, the thermal energy and the lattice energy of the chlorides of alkali metals decrease. The decreasing order is $LiCl>NaCl>KCl>RbCl>CsCl$

Hence, the option C is correct.

D) On moving down the group, the thermal energy and the lattice energy of the oxides of alkali metals decrease. The decreasing order is $L{i}_{2}O>N{a}_{2}O>K_{2}O>R{b}_{2}O$

Hence, the option D is correct.