Q45 · CSIR-NET Chemistry, June 2019
Paper: CSIR-NET June 2019 · Subject: Inorganic Chemistry · Chapter: Coordination Chemistry · Topic: Coordination Chemistry – General · Marks: 2 · Difficulty: Hard
The calculated heat of formation $\left(\Delta \mathrm{H}_{\mathrm{f}}\right)$ for $\mathrm{NaCl}_{2}$ and CaF is
(a)negative for both $\mathrm{NaCl}_{2}$ and $\mathrm{CaF}$
(b)negative for $\mathrm{NaCl}_{2}$ but positive for $\mathrm{CaF}$
(c)positive for $\mathrm{NaCl}_{2}$ but negative for $\mathrm{CaF}$
(d)positive for both $\mathrm{NaCl}_{2}$ and $\mathrm{CaF}$
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
NaCl₂ would need Na's huge second IE — ΔHf positive; CaF (Ca⁺F⁻) has a negative calculated ΔHf (though it disproportionates) (c).
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