11th And 12th > Chemistry
P BLOCK ELEMENTS MCQs
:
D
Compound (A) is - NaBO2
Compound (B) is - Na2B4O7
Compound (C) is - H3BO3
Compound (D) is - B2O3
Compound (E) is - Cu(BO2)2
:
B
Serpeck's process involves -
Al2O3+3C+N2→2AlN+3COAlN+3H2O→Al(OH)3↓+NH32Al(OH)3Δ−→Al2O3+3H2O
:
D
Na2B4O7+7H2O→2B(OH)3+2Na[B(OH)4]
B(OH)3orH3BO3 is an acid and does not react with acid.
Hence Na[B(OH)4] reacts with acid.
:
D
It is pp- pp bonding involving B and F atom responsible for the acidic nature of boron halides as BF3<BCl3<BBr3< BI3 smaller atom shows more back bonding
:
A
K2SO4.AI2(SO4)3.24H2OK2SO4+H2O→K(OH)+H2SO4AI2(SO4)3+H2O→Al(OH)3+H2SO4
:
B
Inert pair effect is the phenomenon in which outer shell (ns2)electrons penetrate to
(n - 1) d electrons and thus becomes closer to nucleus and are more effectively pulled towards nucleus. This results in less availability of ns electrons for bonding. The inert pair effects begins when n = 4 and increases with increasing value of n.
:
A
BF3−6 does not exist because boron does not have vacant d-subshells
:
C
2NaOH+2Al+2H2O→2NaAlO2+3H2
:
C
Due to poor shielding effect of d-electrons, nuclear attraction over valency electrons increases hence atomic size decreases