Chemistry MCQs for NEET — Practice Questions with Answers

Extent of back bonding decreases from BF₃ to BI₃. So, lewis acidic character increases from BF₃ to BI₃. Hence, BF₃ is the weakest lewis acid.

Al does not show inert pair effect due to unavailability of d subshell.

CO2 - acidic,

CO - neutral,

SnO2 - amphoteric,

CaO - basic

In B2H6, there is no direct boron-boron bond. The structure is not similar to that of C2H6 (ethane). The boron atoms are linked through hydrogen bridges, forming a bridged structure. The atoms are not in one plane. Therefore, the correct option is o3: the boron atoms are linked through hydrogen bridges.

H₃BO₃ is not a protonic acid. It can accept one OH^- and converted into [B(OH)₄]^-. So, it is a weak monobasic lewis acid.

The diamond unit cell is a face-centered cubic (FCC) structure with 8 carbon atoms at the corners of the cube. Each carbon atom is shared by 8 neighboring cubes, so the total number of carbon atoms per unit cell is 8.

(c) Due to inert effect the stability of lower oxidation state gradually increase while stability of higher

      oxidation state gradually decreases down the group in elements of group 13th to 15th. So correct 

      orders are :

       (iii) ${\mathrm{Pb}}^{2+}>{\mathrm{Pb}}^{4+}, {\mathrm{Bi}}^{3+}>{\mathrm{Bi}}^{5+}$

       (v) ${\mathrm{Sn}}^{2+}<{\mathrm{Pb}}^{2+}, {\mathrm{Sn}}^{4+}>{\mathrm{Pb}}^{4+}$

Surface of Al forms ${\mathrm{Al}}_2{\mathrm{O}}_3$ on exposure to air and becomes passive.

Each combustion is exothermic.

${\mathrm{Al}}_2{\mathrm{O}}_3+3\mathrm{C}+{\mathrm{N}}_2 \stackrel{}{\to } 2\mathrm{AlN}+3\mathrm{CO}$