Periodic Table & Periodicity — Page 23 | JEE Chemistry

Q221

Given below are the atomic numbers of some group 14 elements. The atomic number of the element with lowest melting point is :

A 14

B 50

C 6

D 82

Correct Answer

Option B

Solution

Order of M.P. of group 14: $\mathrm{C}>\mathrm{Si}>\mathrm{Ge}>\mathrm{Pb}>\mathrm{Sn}$ .tg .tg Element M.P.

( $^\circ$ C) Z = 6 = C 3730 Z = 14 = Si 1410 Z = 32 = Ge 937 Z = 50 = Sn 232 Z = 82 = Pb 327

Q222

The correct orders among the following are Atomic radius :

\mathrm{B} Electronegativity :

\mathrm{Al} Density :

\mathrm{Tl} 1st Ionisation Energy :

\mathrm{In} Choose the correct answer from the options given below:

A B and D Only

B A and B Only

C C and D Only

D A and C Only

Correct Answer

Option A

Solution

.tg .tg B Al Ga In Tl Atomic radius (pm) 88 143 135 167 170 Electronegativity 2 1.5 1.6 1.7 1.8 Density (g/cm $^3$ ) 2.35 2.7 5.9 7.31 11.85 Ionisation Energy (kJ/mol) 801 577 579 558 589

\begin{array}{lc} \text{ Radius Order } & \mathrm{T} \ell>\mathrm{In}>\mathrm{A} \ell>\mathrm{Ga}>\mathrm{B} \\ \text{ EN Order } & \mathrm{B}>\mathrm{T} \ell>\mathrm{In}>\mathrm{Ga}>\mathrm{Al} \\ \text{ Density Order } & \mathrm{T} \ell>\mathrm{In}>\mathrm{Ga}>\mathrm{A} \ell>\mathrm{B} \\ \mathrm{IE}_1 \text{ Order } & \mathrm{B}>\mathrm{T} \ell>\mathrm{Ga}>\mathrm{A} \ell>\mathrm{In} \end{array}

Q223

Match with . (Salt) (Flame colour wavelength)

List - I		List - II
(a)	LiCl	(i)	455.5 nm
(b)	NaCl	(ii)	670.8 nm
(c)	RbCl	(iii)	780.0 nm
(d)	CsCl	(iv)	589.2 nm

A (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)

B (a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)

C (a)-(i), (b)-(iv), (c)-(ii), (d)-(iii)

D (a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)

Correct Answer

Option D

Solution

.tg .tg Alkali metal Colour (Flame) $\lambda$ (nm) Li Crimson red 670.8 Na Yellow 589.2 Rb Red, violet 780.0 Cs Blue 455.5 Alkali metals have very low value of ionisation energy as compared to other metals.

So, alkali metals easily get excited and impart colour to flame.

Hence, Rb is most excited and having high value of wavelength in all alkali metals.

Q224

Which one of the following order represents the correct sequence of the increasing basic nature of the given oxides ?

A MgO < K2O < Al2O3 < Na2O

B Al2O3 < MgO < Na2O < K2O

C Na2O < K2O < MgO < Al2O3

D K2O < Na2O < Al2O3 < MgO

Correct Answer

Option B

Solution

You should know that, (1)

\,\,\,

In a period, from left to right the acidic strength increases that mean basic nature decreases. (2)

\,\,\,

In a group, from top to bottom the basic nature increases that means acidic nature decreases.

Na, Mg, Al and K are present in periodic table like this : - .tg .tg Group 1 Group 2 Group 13 Period 3 Na Mg .....

Al Period 4 K So, you can see Na, Mg and Al are present in same period so the order of basic nature among Na, Mg and Al is Na > Mg > Al.

And Na and K are from same group so basic nature of K > Na.

So the correct order of oxides Al2O3 < MgO < Na2O < K2O

Q225

Match with : .tg .tg

List - I		List - II
(a)	Sodium hydride	(i)	Lewis acid
(b)	Silane	(ii)	Saline hydride
(c)	Vanadium hydride	(iii)	Molecular hydride
(d)	Aluminium hydride	(iv)	Non-stoichiometric hydride Correct answer is :

A (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)

B (a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)

C (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)

D (a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)

Correct Answer

Option A

Solution

.tg .tg List-I List-II (a) Sodium hydride (ii) Saline hydride (b) Silane (iii) Molecular hydride (c) Vanadium hydride (iv) Non-stoichiometric hydride (d) Aluminium hydride (i) Lewis acid

Q226

The size of the iso-electronic species Cl–, Ar and Ca2+ is affected by :

A electron-electron interaction in the outer orbitals

B Principal quantum number of valence shell

C nuclear charge

D azimuthal quantum number of valence shell

Correct Answer

Option C

Solution

Cl- Ar Ca+2 Protons 17 18 20 Electrons 18 18 18 Nuclear charge means number of protons present in the nucleus.

Here maximum number of protons present in the Ca+2 ion, so the attraction towards those 18 electrons wll be most by the nucleus of the Ca+2 ion.

That is why size of the Ca+2 ion wll be least because of highest nuclear charge.

Q227

Lithium nitrate and sodium nitrate, when heated separately, respectively, give :

A

\mathrm{LiNO}_{2}

and

\mathrm{NaNO}_{2}

B

\mathrm{Li}_{2} \mathrm{O}

and

\mathrm{Na}_{2} \mathrm{O}

C

\mathrm{Li}_{2} \mathrm{O}

and

\mathrm{NaNO}_{2}

D

\mathrm{LiNO}_{2}

and

\mathrm{Na}_{2} \mathrm{O}

Correct Answer

Option C

Solution

\mathrm{Li}_{2} \mathrm{O}, \mathrm{NaNO}_{2}

As per NCERT lithium nitrate when heated gives lithium oxide,

\mathrm{Li}_{2} \mathrm{O}

. Whereas other alkali metal nitrates decompose to give the corresponding nitrite.

4 \mathrm{LiNO}_{3} \longrightarrow 2 \mathrm{Li}_{2} \mathrm{O}+4 \mathrm{NO}_{2}+\mathrm{O}_{2}

2 \mathrm{NaNO}_{3} \longrightarrow 2 \mathrm{NaNO}_{2}+\mathrm{O}_{2}

However, the decomposition product of

\mathrm{NaNO}_{3}

is temperature dependent process as shown in the below reaction.

\mathrm{NaNO}_{3} \underset{500^{\circ} \mathrm{C}}{\stackrel{\Delta}{\longrightarrow}} \mathrm{NaNO}_{2}(\mathrm{~s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g})

\Delta \downarrow, 800^{\circ} \mathrm{C}

\mathrm{Na}_{2} \mathrm{O}(\mathrm{s})+\mathrm{N}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g})

As the temperature is not mentioned, we can go by the answer. (C)

Q228

The set representing the correct order of ionic radius is :

A

N{a^ + } > L{i^ + } > M{g^{2 + }} > B{e^{2 + }}

B

L{i^ + } > N{a^ + } > M{g^{2 + }} > B{e^{2 + }}

C

M{g^{2 + }} > B{e^{2 + }} > L{i^ + } > N{a^ + }

D

L{i^ + } > B{e^{2 + }} > N{a^ + } > M{g^{2 + }}

Correct Answer

Option A

Solution

In periodic table

Li, Na, Mg, Be

are present in following ways :- .tg .tg Group 1 Group 2 Li Be Na Mg Note :

(1)\,\,\,

In periodic table from left to right the size of element decreases.

(2)\,\,\,

In periodic table, from top to bottom size of element increases. So,

B{e^{ + 2}}

will be the smallest in size. Among

L{i^ + }

and

N{a^ + },

size of

N{a^ + } > L{i^ + }

and among

B{e^{ + 2}}

and

M{g^{ + 2}},

size of

M{g^{ + 2}} > B{e^{ + 2}}

. Note : Size of

L{i^ + } > M{g^{ + 2}},

this is a exception case. So, the correct order will be,

N{a^ + } > L{i^ + } > M{g^{ + 2}} > B{e^{ + 2}}

Q229

The substance not likely to contain CaCO3 is :

A calcined gypsum

B sea shells

C dolomite

D a marble statue

Correct Answer

Option A

Solution

Gypsum is

\,\,CaS{O_4}.2{H_2}O

Q230

The atomic number of the element unnilennium is :

A 109

B 102

C 119

D 108

Correct Answer

Option A

Solution

For Unnilennium IUPAC symbol – Une Atomic No. – 109