Q1Arrange the following in incresing lattice energy-
(1)BeCO3,MbCO3,CaCO3,SrCO3,BaCO3
(2)Li2CO3,Na2CO3,K2CO3
(3)LiCl,NaCl,KCl
(4)LiF,LiBr,LiI
Q2The lattice energy of CaO is -3460kJ/mol ;the lattice energy of K2O is -2240kJ/mol.Account for the difference.
106Lattice energy can be equivalently denoted as the attraction between the ions. i.e. F=kqcationqanion/(rcat+ran)2
In (1) the anion is same. So the lattice energy will depend on charge density of cation hence BeCO3>MgCO3>CaCO3>SrCO3>BaCO3
In (2) similarly, Li2CO3>Na2CO3>K2CO3
In (3) LiCl>NaCl>KCl
In (4) cation is same so lattice energy depends on charge density of anion .. Hence LiF>LiBr>LiI
106Q2.. As in both cases anion is same so the difference in lattice energy occurs due to the cations
Now Ca2+ is smaller in size than K+ and its charge is more.. Hence its charge density is more .So lattice energy of CaO is more than K2O
1q1.)(1) can be done using fajan's rule.
it tells, decrease in size of cations increases covalency.
the more covalent the moolecule, the lesser the lattice energy.
so, BeCO3<MgCO3<CaCO3<SrCO3<BaCO3
1just remember
LE inversly proporionnal to (r++r-)
& directly proportional to product of charges of cation & anion
so u will get what ashish has got
@ skygal
"the more covalent the moolecule, the lesser the lattice energy."
i think this cannot be generalised
