Give important trends and anomalous properties of boron.
Give important trends and anomalous properties of boron.
Certain important trends can be observed in the chemical behaviour of group-$13$ elements. The trichlorides, bromides and iodides of all these elements being covalent in nature are hydrolysed in water.
Species like tetrahedral $\left[\mathrm{M}(\mathrm{OH})_{4}\right]^{-}$and octahedral $\left[\mathrm{M}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}$, except in boron, exist in aqueous medium.
The monomeric trihalides, being electron deficient, are strong Lewis acids. Boron trifluoride easily reacts with Lewis bases such as $\mathrm{NH}_{3}$ to complete octet around boron.
It is due to the absence of $d$-orbitals that the maximum covalence of $B$ is $4$ . Since the $d$ orbitals are available with $\mathrm{Al}$ and other elements, the maximum covalence can be expected beyond $4$.
Most of the other metal halides (e.g., $\mathrm{AlCl}_{3}$ ) are dimerised through halogen bridging (e.g., $\mathrm{Al}_{2} \mathrm{Cl}_{6}$ ). The metal species completes its octet by accepting electrons from halogen in these halogen bridged molecules.
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Give uses of $LiBH_4$ and $NaBH_4$.
Give uses of $LiBH_4$ and $NaBH_4$.
Which among the following statement(s) is(are) true for the extraction of aluminium from bauxite?
$(A)$ Hydrated $Al _2 O _3$ precipitates, when $CO _2$ is bubbled through a solution of sodium aluminate.
$(B)$ Addition of $Na _3 AlF _6$ lowers the melting point of alumina.
$(C)$ $CO _2$ is evolved at the anode during electrolysis.
$(D)$ The cathode is a steel vessel with a lining of carbon.
Which among the following statement(s) is(are) true for the extraction of aluminium from bauxite?
$(A)$ Hydrated $Al _2 O _3$ precipitates, when $CO _2$ is bubbled through a solution of sodium aluminate.
$(B)$ Addition of $Na _3 AlF _6$ lowers the melting point of alumina.
$(C)$ $CO _2$ is evolved at the anode during electrolysis.
$(D)$ The cathode is a steel vessel with a lining of carbon.
- [IIT 2020]
$A{l_2}{O_3}$ formation involves evolution of a large quantity of heat, which makes its use in
$A{l_2}{O_3}$ formation involves evolution of a large quantity of heat, which makes its use in
$BCl_3$ does not exist as dimer but $BH_3$ exist as dimer $(B_2H_6)$ becuase
$BCl_3$ does not exist as dimer but $BH_3$ exist as dimer $(B_2H_6)$ becuase