JEE PYQ: S Block Elements Question 12
Question 12 - 2021 (24 Feb Shift 2)
The Correct set from the following in which both pairs are in correct order of melting point is:
(a) LiF > LiCl; NaCl > MgO (b) LiF > LiCl; MgO > NaCl (c) LiCl > LiF; NaCl > MgO (d) LiCl > LiF; MgO > NaCl
Show Answer
Answer: (b)
Solution
M.P. $\propto$ Lattice energy $= \frac{Kq_1q_2}{r^+ + r^-}$. LiF has a smaller anion than LiCl, so higher lattice energy and higher melting point: LiF > LiCl. MgO has higher charges ($2+, 2-$) than NaCl ($1+, 1-$), so MgO > NaCl.
BETA
