MCQ
Correct Lewis acidity order of $BX_3$ is
- ✓$BF_3 < BCl_3 < BBr_3 < BI_3$
- B$BF_3 > BCl_3 > BBr_3 > BI_3$
- C$BCl_3< BBr_3 < BI_3 < BF_3$
- D$BF_3 < BI_3 < BBr_3 < BCl_3$
(ii) Size of halides increase down the group, hence the ability of back bonding decreases making the molecule more acidic.
Hence, correct order of Lewis acid for boron-halides is $\mathrm{Bl}_{3}>\mathrm{BBr}_{3}>\mathrm{BCl}_{3}>\mathrm{BF}_{3}$
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(Plank's const. $ h = 6. \times 10^{-34}\, Js\,;$ mass of electron $= 9.1091 \times 10^{-31}\, kg\,;$ charge of electron $e= 1.60210 \times 10^{-19}\, C\,;$ permittivity of vaccum $\in _0 = 8.854185 \times 10^{-12} \,kg^{-1} \,m^{-3} A^2$)