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The p-Block Elements

Multiple Choice Questions

271.

In silica (SiO₂), each silicon atom is bonded to

two oxygen atoms
four oxygen atoms
one silicon and two oxygen atoms
one silicon and four oxygen atoms

272.

C-C bond length is maximum in

diamond
graphite
naphthalene
fullerone

273.

Dry ice is

Solid H₂O
Solid CO₂
Solid N₂O₄
Solid NH₃

274.

When borax is heated strongly, it gives

BaBO₂
B₂O₃
B₃N₃H₆
Na₂B₄O₇

275.

Sindhur, an oxide of lead, is an example of ............. oxide.

basic
super
mixed
amphoteric

276.
The magnetic nature of boron molecule is same as the magnetic nature of

nitrogen molecule

carbon molecule

unipositive nitrogen molecule

oxide ion

unipositive nitrogen molecule

The magnetic nature of boron molecule is same as the magnetic nature of unipositive nitrogen molecule.

Boron - B₂ = (5 + 5 = 10) = σ1s², $\overset{*}{σ} 1 s^{2}, σ 2 s^{2}, \overset{*}{σ} 2 s^{2}, π 2 p_{x}^{1} \approx π 2 p_{y}^{1}$

(Since, two unpaired electrons are present, the boron molecule is paramagnetic).

Nitrogen - $N_{2}^{+} = (7 + 7 - 1 = 13) = σ 1 s^{2}, \overset{*}{σ} 1 s^{2}, σ 2 s^{2}, \overset{*}{σ} 2 s^{2}, π 2 p_{x}^{2} \approx π 2 p_{y}^{2}, σ 2 p_{z}^{1}$

(Since, one unpaired electron, it is paramagentic).

277.

Which of the following is not a true alum?

Na₂SO₄.Al₂(SO₄)₃.24H₂O
MgSO₄.Cr₂(SO₄)₃.24H₂O
K₂SO₄.Cr₂(SO₄)₃.24H₂O
(NH₄)₂SO₄.Fe(SO₄)₃.24H₂O

278.

The densities of graphite and diamond at 298 K are 2.25 and 3.31 g cm^-3 respectively. If the standard free energy difference is 1895 J mol^-1, the pressure at which graphite will be transformed into diamond is