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Q.1
Hard
Chemistry 03 Apr 2026
Which of the following substances will have the lowest lattice enthalpy among ionic compounds?
Correct Answer: C. CsI
EXPLANATION
Lattice enthalpy depends inversely on ionic radius and directly on ionic charge.
CsI has the lowest lattice enthalpy (~604 kJ/mol) because both Cs⁺ and I⁻ are large ions with 1+ and 1- charges respectively.
In contrast, MgO has very high lattice enthalpy due to small, highly charged ions (Mg²⁺ and O²⁻), while NaCl and CaF₂ have intermediate values.
Q.2
Hard
Chemistry 03 Apr 2026
Which of the following compounds exhibits both ionic and covalent bonding characteristics and is commonly used in coordination chemistry?
Correct Answer: B. Potassium hexacyanoferrate(III)
EXPLANATION
Potassium hexacyanoferrate(III) contains both ionic bonds (between K⁺ and the [Fe(CN)₆]³⁻ complex) and covalent bonds (between Fe and CN ligands, and within the CN groups).
This complex salt is extensively used in coordination chemistry and analytical procedures like the Prussian blue test.
