Chemistry Test 188

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Chemistry Test 188

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Weekly Quiz Competition

Question 1
4 / -1

Select the incorrect statement about the XeF₆.

A
It has capped octahedron or distorted octahedral structure with one lone pair.

B
In various non-aqueous solvents it forms a tetramer Xe₄F₂₄.

C
Solid Xenon hexafluoride is polymorphic.

D
None of these

Solution

In tetramer, four square pyramidal XeF5+ ions are joined to two similar ions by means of two bridging F- ions. The Xe-F distances are 1.84 A on the square pyramidal units and 2.23 A and 2.60 A in the bridging groups. The solid has various crystalline forms, of which three are tetrameric and a fourth has both hexamers and tetramers.
Question 2
4 / -1

Based on the Valence Shell Electron Pair Repulsion (VSEPR) model, what is the geometry around the sulphur, carbon and nitrogen in the thiourea – S , S – dioxide, O₂SC(NH₂)₂ ? (consider the Lewis structure with zero formal charges on all atoms).

A
Trigonal planar, T–shaped, trigonal planar respectively.

B
T-shaped, trigonal planar, trigonal planar respectively.

C
Trigonal planar, trigonal planar, trigonal pyramidal respectively.

D
Trigonal planar, trigonal planar, trigonal planar respectively.

Solution
Question 3
4 / -1

The following flow diagram represents the manufacturing of sodium carbonate

Which of the following options describes the reagents, products and reaction conditions (given in parentheses)?

A

B

C

D

Solution
Question 4
4 / -1

When boron is fused with potassium hydroxide which pair of species are formed ?

A

B

C

D

Solution
Question 5
4 / -1

B₂H₆+ NH₃ → Addition compound In the above sequence Y and Z are respectively :

A
boron nitride, H₂

B
boron and hydrogen

C
boron nitride and hydrogen

D
borazine and hydrogen

Solution
Question 6
4 / -1

Orthosilicate ions, (SiO₄^4-) undergo polycondensation to froms pyrosilicate [O₃Si - O - SiO₃]^6-, in presence of:

A
acid

B
water

C
both (A) and (B)

D
none of these

Solution

2SiO₄^4- + H₂O → [O₃Si - O - SiO₃]^6- + 2OH^- ; 2SiO₄^4- + 2H⁺ → [O₃Si - O - SiO₃]^6- + H₂O.
Question 7
4 / -1

Which of the following statements is correct ?

A
BrF₃ molecule is a slightly "bent T" with each FBrF (except axial FBrF) bond angle of 86º not 90º.

B
In OSF₄, the axial FSF angle and equatorial FSF angles are perfectly 180º and 120º respectively.

C
In methylene sulphur tetrafluoride CH₂SF₄, the hydrogen atoms are in a horizontal plane with the axial fluorine atoms.

D
All of these.

Solution

Hydrogen atoms lie in the CSF₂ axial plane. We know that the it bond involving a p-orbital on the carbon atom must lie in the equatorial plane of the molecule.
Question 8
4 / -1

The hybridisation and geometry of the anion of ICl₃ in liquid phase is :

A
sp³ and bent

B
sp³d² and square planar

C
sp³d and see–saw

D
sp³ and tetrahedral

Solution
Question 9
4 / -1

Which of the following orders is correct for the size ?

(1) Mg²⁺ < Na⁺ < F^– < Al

(2) Al³⁺ < Mg²⁺ < Li⁺ < K⁺

(3) Fe⁴⁺ < Fe³⁺ < Fe²⁺ < Fe

(4) Mg > Al > Si > P

A
(1), (2) & (3)

B
(2), (3) & (4)

C
(1), (3) & (5)

D
(1), (2), (3) & (4)

Solution

(1) Mg²⁺, Na⁺ and F^- are isoelectronic and thus follows the order ₁₂Mg²⁺ < ₁₁Na⁺ < gF^-. Al belongs to third period and has no charge so it is largest. Na⁺ = 102 pm; Mg²⁺ = 72 pm ; Al = 143 pm, F- = 133 pm.

(2) K⁺ has more number of shells than Mg²⁺ and Al³⁺. Al³⁺ and Mg²⁺ are isoelectronic but Al³⁺ has higher nuclear charge so Al³⁺ < Mg²⁺. Mg²⁺ and Li⁺ has diagonal relationship. But due to +2 charge in Mg²⁺, the Mg²⁺ is smaller than Li⁺ Hence Al³⁺ is the smallest one. K⁺ =1.38 Å, Li²⁺ = 0.76 Å Mg²⁺ = 0.72 Å and Al³⁺ = 0.535 Å.

(3) As the number of electrons are lost, the attraction between valence shell electrons and nucleus increases. As a consequence of this the electrons are pulled closer to the nucleus leading to the contraction in size of ions.

(4) Across the period the nuclear charge increases and thus the size of atoms decreases. Mg = 160 pm; Al = 143 pm; Si = 118 ; P = 110 pm.
Question 10
4 / -1

Which reactions involves a change in the electron–pair geometry for the under lined atoms ?

A

B

C

D

Solution