NEET Practice Questions (MCQs) with Answers & Solutions

$H_3BO_3$ (boric acid) is a weak monobasic acid, not a strong tribasic acid. It is prepared by acidifying an aqueous solution of borax and has a layer structure with $BO_3^{3-}$ units joined by hydrogen bonds. It acts as a Lewis acid by accepting hydroxyl ions rather than donating protons.

In diborane ($B_2H_6$), boron atoms are $sp^3$ hybridized. Each boron forms three $sp^3$ hybrid orbitals that overlap with hydrogen orbitals to form bonds, including the unique three-center two-electron bonds (banana bonds) in diborane.

In diborane (B₂H₆), there are two bridging hydrogen atoms and four terminal hydrogen atoms. Each boron atom forms three center-two electron bonds with the bridging hydrogens and normal two-center two-electron bonds with the terminal hydrogens. Therefore, not all B-H bonds are similar; the bridging B-H bonds are different from the terminal B-H bonds.

Gallium is a soft, heavy metal that melts at approximately 30°C. It is commonly used in making heat-sensitive thermometers because it remains in liquid form over a wide temperature range.

In the given reaction, $ B_2O_3 + C + Cl_2 ightarrow A + CO $, the product 'A' is $ BCl_3 $. The reaction is a standard method for producing boron trichloride by reacting boron oxide with carbon and chlorine gas.

The acidity of oxides generally increases across the period and decreases down the group in the periodic table. $B_2O_3$ (Boron trioxide) is the most acidic among the given options because Boron is to the right in the periodic table compared to Phosphorus, Arsenic, and Antimony. As we move from left to right across a period, the acidic character of oxides increases.

When an aqueous solution of aluminium chloride ($AlCl_3$) is heated to dryness, it undergoes hydrolysis to form aluminium oxide ($Al_2O_3$). This happens because $AlCl_3$ hydrolyzes in water to form $Al(OH)_3$, which upon heating, dehydrates to form $Al_2O_3$.

$B_2H_6$ (Diborane) is an electron-deficient molecule because Boron has only three electrons in its valence shell and forms three covalent bonds. In $B_2H_6$, there are not enough electrons to form conventional 2-center 2-electron bonds for all atoms, leading to the formation of multi-center bonds (3-center 2-electron bonds) which are characteristic of electron-deficient compounds.

Diborane ( ext{B}_2 ext{H}_6) has a unique structure where there are four terminal hydrogen atoms bonded to boron atoms via conventional 2-center-2-electron (2c-2e) bonds. Additionally, there are two bridging hydrogen atoms that connect the boron atoms via 3-center-2-electron (3c-2e) bonds. This can be visualized as each boron atom forming two normal bonds with the terminal hydrogen atoms and sharing two more hydrogen atoms with the other boron atom in a bridged configuration.