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
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.
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5 Answers
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
106
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
