M.C.Q (1 Marks)

MCQ 1511 Mark

The colour of $\mathrm{Co}\left(\mathrm{BO}_2\right)_2$ is:

✓
Blue
B
Green
C
Yellow
D
Violet

Answer

Correct option: A.

Blue

When the glassy bead is dipped in $Co$ salt and heated, blue coloured bead is formed.

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MCQ 1521 Mark

Ionisation enthalpy $(\triangle _i \ H_1\ kJ\ mol^{-1})$ for the elements of Group $13$ follows the order.

A
$\text{B > Al > Ga > In > Tl.}$
B
$\text{B < Al < Ga < In < Tl.}$
C
$\text{B < Al > Ga < In > Tl.}$
✓
$\text{B > Al < Ga > In < Tl.}$

Answer

Correct option: D.

$\text{B > Al < Ga > In < Tl.}$

On moving down the group from $B$ to $TI$, a regular decreasing trend in the ionisation energy values is not observed.
$\ \ \text{B}\ \ \ \ \ \text{Al}\ \ \ \ \ \text{Ga}\ \ \ \ \ \text{In}\ \ \ \ \ \ \text{Tl}\\801\ \ \ 577\ \ \ 579\ \ \ \ 558\ \ \ \ 589\ \ \ \ \ \text{kJ mol}^{-1}$
In Ga, there are ten d-electrons in the penultimate shell which screen the nuclear charge less effectively and thus, outer electron is held firmly. As a result, the ionisation energy of both $Al$ and $Ga$ is nearly the same. The increase in ionisation energy from In to $Tl$ is due to poor screening effect of $14f$ electrons present in the inner shell.

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MCQ 1531 Mark

The second period elements of $p-$ block starting from boron, are restricted to a maximum covalency of :

A
Four $($using $1s, 2s $ and two $2p$ orbitals$).$
B
Six $($using $1s$ and $2s -$ orbitals$)$.
✓
Four $ ($using $2s$ and three $2p$ orbitals$).$
D
Six $($using $1s$ and three $2p$ orbitals$)$.

Answer

Correct option: C.

Four $ ($using $2s$ and three $2p$ orbitals$).$

The second period elements of $p-$ block starting from boron are restricted to a maximum covalency of four $($using one $2s$ and three $2p$ orbitals$).$

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MCQ 1541 Mark

The platinum wire which is used in borax bead test is dipped in:

✓
powdered borax
B
metaboric acid
C
orthoboric acid
D
all

Answer

Correct option: A.

powdered borax

The borax bead test is the most common. A small loop is formed at the end of a platinum wire. The loop is cleaned with concentrated hydrochloric acid and dipped in powdered borax, then heated in the flame of a Bunsen burner until the borax melts, forming a bead.

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MCQ 1551 Mark

The aqueous solution of borax turns red litmus to :

A
Blue
✓
No Change
C
Red
D
White

Answer

Correct option: B.

No Change

This is because of the alkanline nature of the aqueous solution of borax.

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MCQ 1561 Mark

The increasing order of atomic radius:

A
$\text{Al < Ga < In < TI.}$
✓
$\text{Ga < Al < In < TI.}$
C
$\text{Al < In < Ga < TI.}$
D
$\text{Al < Ga < TI < In.}$

Answer

Correct option: B.

$\text{Ga < Al < In < TI.}$

$Ga$ is smaller than $'Al\ '$ due to poor shelling effect of $d-$electron effective nuclear charge increases.

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MCQ 1571 Mark

Which of the following is solid at room temperature?

A
$\text{CO}$
B
$ \mathrm{CO}_2 $
✓
$ \mathrm{SiO}_2 $
D
$\mathrm{OF}_2 $

Answer

Correct option: C.

$ \mathrm{SiO}_2 $

Silicon dioxide involves covalent $\text{Si−O}$ bonds. It has strong van der waal's forces of interactions and thus exists as solids.

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MCQ 1581 Mark

The property which does not support anomalous behaviour of boron is :

✓
Formation of trihalides.
B
High ionisation energy.
C
Small size.
D
High electronegativity.

Answer

Correct option: A.

Formation of trihalides.

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MCQ 1591 Mark

Graphite cleaves easily between the layers. Thus, it is :

A
Soft.
B
Slippery.
✓
Both $(a)$ and $(b).$
D
None of these.

Answer

Correct option: C.

Both $(a)$ and $(b).$

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MCQ 1601 Mark

The colour of blue glass is due to the presence of oxide of :

A
Chromium
✓
Cobalt
C
Gold
D
Silver

Answer

Correct option: B.

Cobalt

Cobalt is a very intense glass colorant and very little is required to show a noticeable amount of colour. Colour of Cobalt glass is blue.

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MCQ 1611 Mark

Borax is known as :

A
Sodium borate.
B
Sodium tetra borate.
C
isodium tetra borate.
✓
All

Answer

Correct option: D.

All

Borax : $\mathrm{Na}_2\left[\mathrm{~B}_4 \mathrm{O}_5(\mathrm{OH})_4\right] \cdot 8 \mathrm{H}_2 \mathrm{O}$.

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MCQ 1621 Mark

Group $13$ elements are attacked by non$-$oxidising acids except:

A
Aluminium
B
Gallium
C
Indium
✓
Boron

Answer

Correct option: D.

Boron

Boron is not attacked by non-oxidising acids such as $\text{HCl}$ but reacts with oxidising acids such as conc. $\mathrm{HNO}_3$ and conc. $\mathrm{H}_2 \mathrm{SO}_4$ forming boric acid.
Boron, being chemically a non$-$metal, is resistant to attack by non$-$oxidising acids but the other members of the group react with non$-$oxidising acids as typical metals and evolve hydrogen.

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MCQ 1631 Mark

Aluminium is much more reactive than iron because its standard reduction potential is higher than iron. Still, aluminium is less easily corroded than iron because :

A
Aluminium reacts with atmospheric carbon dioxide to form a self$-$protective layer of $\ce{Al_2O_3}$.
✓
It has a higher reducing power and forms a self protective layer of $\ce{Al_2O_3}$.
C
it has a higher reducing power and does not react with oxygen so easily.
D
both $A$ and $B.$

Answer

Correct option: B.

It has a higher reducing power and forms a self protective layer of $\ce{Al_2O_3}$.

Aluminium is much more reactive than iron because its standard reduction potential is higher than iron. However, aluminium is still less easily corroded than iron because oxygen forms a protective oxide layer of $\ce{Al_2O_3}$ on its surfac.

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MCQ 1641 Mark

Which of the following strongest lewis acid :

A
$\mathrm{BCl}_3$
B
$\mathrm{BF}_3$
✓
$\mathrm{BI}_3$
D
$\mathrm{BBr}_3$

Answer

Correct option: C.

$\mathrm{BI}_3$

$\mathrm{BI}_3$ because backbonding is least effective between $5p-5p$ overlapping.

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Chemistry M.C.Q (1 Marks)