Periodic Table & Periodicity — Page 7 | NEET Chemistry

Q61

The ionic radius of Na+ ions is 1.02

\mathop A\limits^o

. The ionic radii (in

\mathop A\limits^o

) of Mg2+ and Al3+, respectively, are

A 1.05 and 0.99

B 0.72 and 0.54

C 0.85 and 0.99

D 0.68 and 0.72

Correct Answer

Option B

Solution

The ionic radii (in

\mathop A\limits^o

) of

\text{Mg}^{2+}

and

\text{Al}^{3+}

, respectively, are: Option B:

0.72 \mathop A\limits^o

for

\text{Mg}^{2+}

0.54 \mathop A\limits^o

for

\text{Al}^{3+}

Q62

Given below are two statements : Statement I : None of the alkaline earth metal hydroxides dissolve in alkali. Statement II : Solubility of alkaline earth metal hydroxides in water increases down the group. In the light of the above statements, choose the most appropriate answer from the options given below :

A Statement I is correct but Statement II is incorrect.

B Statement I is incorrect but Statement II is correct.

C Statement I and Statement II both are incorrect.

D Statement I and Statement II both are correct.

Correct Answer

Option B

Solution

Statement - I is incorrect Be(OH)2 dissolve in alkali due to it's amphoteric nature.

Statement - II is correct Solubility of alkaline earth metal hydroxide in water increases down the group due to rapid decreases in lattice energy as compared to hydration energy.

Q63

Inert gases have positive electron gain enthalpy. Its correct order is :

A He < Ne < Kr < Xe

B He < Xe < Kr < Ne

C Xe < Kr < Ne < He

D He < Kr < Xe < Ne

Correct Answer

Option B

Solution

.tg .tg $\begin{gathered}\text{ Electron } \\\text{ gain }\end{gathered}$ $\mathrm{He}$ $\mathrm{Ne}$ $\mathrm{Ar}$ $\mathrm{Kr}$ $\mathrm{Xe}$ $\begin{gathered}\text{ Enthalpyl } / \\\mathrm{kJ} ~\mathrm{mol}^{-1}\end{gathered}$ 48 116 96 96 77

Q64

Consider the following elements

\mathrm{In}, \mathrm{Tl}, \mathrm{Al}, \mathrm{Pb}, \mathrm{Sn}

and Ge . The most stable oxidation states of elements with highest and lowest first ionisation enthalpies, respectively, are

A +4 and +1

B +4 and +3

C +1 and +4

D +2 and +3

Correct Answer

Option B

Solution

Among $\mathrm{Al}, \mathrm{In}, \mathrm{Tl}, \mathrm{Ge}, \mathrm{Sn}, \mathrm{Pb}$ , the metal having highest $\mathrm{IE}_1$ is Ge and lowest $\mathrm{IE}_1$ is $\mathrm{In}$ .

Most stable oxidation state of Ge is +4 and In is +3 .

Q65

A s-block element (M) reacts with oxygen to form an oxide of the formula MO2. The oxide is pale yellow in colour and paramagnetic. The element (M) is :

A Mg

B Na

C Ca

D K

Correct Answer

Option D

Solution

The element (M) is potassium (K).

It reacts with O2 to form KO2, which is paramagnetic in nature.

All other elements form oxides or peroxides which are diamagnetic in nature.

Q66

Given below are two statements : Statement (I) : The

4 \mathrm{f}

and

5 \mathrm{f}

- series of elements are placed separately in the Periodic table to preserve the principle of classification. Statement (II) : S-block elements can be found in pure form in nature. In the light of the above statements, choose the most appropriate answer from the options given below :

A Statement I is false but Statement II is true

B Both Statement I and Statement II are true

C Statement I is true but Statement II is false

D Both Statement I and Statement II are false

Correct Answer

Option C

Solution

Statement I is correct because the 4f and 5f series elements, commonly referred to as the lanthanides and actinides, respectively, have unique properties and configurations that distinguish them from other elements.

Placing them separately in the Periodic table helps to maintain the orderly classification based on atomic numbers and avoids disrupting the pattern established by the periodic law.Statement II is incorrect because s-block elements, which include Group 1 (alkali metals) and Group 2 (alkaline earth metals), are indeed highly reactive.

They typically do not exist in their pure form in nature due to their reactivity.

Instead, they are mostly found in compound forms, combined with other elements.

For instance, sodium (Na) and potassium (K) from Group 1 react with water and are usually found as salts, not in their metallic, pure state.

Q67

Match List I with List II .tg .tg LIST I LIST II A. Melting Point

[\mathrm{K}]

I.

\mathrm{T} 1>\mathrm{In}>\mathrm{Ga}>\mathrm{A} 1>\mathrm{B}

B. Ionic Radius

[\mathrm{M}^{+3} / \mathrm{pm}]

II.

\mathrm{B}>\mathrm{T} 1>\mathrm{Al} \approx \mathrm{Ga}>\mathrm{In}

C.

\Delta_{\mathrm{i}} \mathrm{H}_1[\mathrm{~kJ} \mathrm{~mol}^{-1}]

III.

\mathrm{T} 1>\mathrm{In}>\mathrm{Al}>\mathrm{Ga}>\mathrm{B}

D. Atomic Radius [pm] IV.

\mathrm{B}>\mathrm{A} 1>\mathrm{T} 1>\mathrm{In}>\mathrm{Ga}

Choose the correct answer from the options given below:

A A-IV, B-I, C-II, D-III

B A-I, B-II, C-III, D-IV

C A-III, B-IV, C-I, D-II

D A-II, B-III, C-IV, D-I

Correct Answer

Option A

Solution

Melting point :

\mathrm{B}>\mathrm{A} \ell>\mathrm{T} \ell>\mathrm{In}>\mathrm{Ga}

Ionic radius

(\mathrm{M}^{+3} / \mathrm{pm}): \mathrm{T} \ell>\mathrm{In}>\mathrm{Ga}>\mathrm{A} \ell>\mathrm{B}

\left(\Delta_{\mathrm{IE}} \mathrm{H}\right)_1\left[\frac{\mathrm{kJ}}{\mathrm{mol}}\right]: \mathrm{B}>\mathrm{T} \ell>\mathrm{A} \ell \approx \mathrm{Ga}>\mathrm{In}

Atomic radius (in

\mathrm{pm}

) :

\mathrm{T} \ell>\mathrm{In}>\mathrm{A} \ell>\mathrm{Ga}>\mathrm{B}

Q68

Which of the following statements are correct? A. The process of adding an electron to a neutral gaseous atom is always exothermic. B. The process of removing an electron from an isolated gaseous atom is always endothermic. C. The

1^{\text{st }}

ionization energy of boron is less than that of beryllium. D. The electronegativity of C is 2.5 in

\mathrm{CH}_4

and

\mathrm{CCl}_4

E. Li is the most electropositive among elements of group I. Choose the correct answer from the options given below:

A A, C and D Only

B B and C Only

C B and D Only

D B, C and E Only

Correct Answer

Option B

Solution

(A) The process of adding an $\mathrm{e}^{-}$ to a neutral gaseous atom is not always exothermic it may be exothermic or endothermic.

$\begin{array}{cc}\text{ (C) } \mathrm{Be} & \mathrm{B} \\ 1 \mathrm{~s}^2 2 s^2 & 1 s^2 2 s^2 2 p^1\end{array}$ In Be 2s subshell in fully filled So, need high energy to remove $\mathrm{e}^{-}$ as compared to B . due to partially positive charge $z_{\text{eff }} \uparrow, \mathrm{EN} \uparrow$ So, EN of $\mathrm{C} \Rightarrow \mathrm{CCl}_4>\mathrm{CH}_4$ (E) Cs is most electropositive.

Q69

The main oxides formed on combustion of Li, Na and K in excess of air are, respectively :

A LiO2, Na2O2 and K2O

B Li2O2, Na2O2 and KO2

C Li2O, Na2O2 and KO2

D Li2O, Na2O and KO2

Correct Answer

Option C

Solution

On heating with excess of air

Li,

Na

and

K

forms following oxides

4Li + {O_2}\,\,\overset{\,}\longrightarrow \,\,\mathop {2L{i_2}O\,\,\,\,\,\,\,\,\,\,}\limits_{Lithium\,\,\,\,monoxide} \,

2Na + {O_2}\,\,\overset{{575\,\,K}}\longrightarrow \,\,\mathop {N{a_2}{O_2}\,\,\,\,\,\,\,\,\,\,\,}\limits_{Sodium\,\,\,peroxide}

K + {O_2}\,\,\overset{\,}\longrightarrow \,\,\mathop {K{O_2}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}\limits_{Potassium\,\,\,\sup eroxise}

Q70

B has a smaller first ionization enthalpy than Be. Consider the following statements : (I) It is easier to remove 2p electron than 2s electron (II) 2p electron of B is more shielded from the nucleus by the inner core of electrons than the 2s electrons of Be. (III) 2s electron has more penetration power than 2p electron. (IV) atomic radius of B is more than Be (Atomic number B = 5, Be = 4) The correct statements are :

A (I), (III) and (IV)

B (II), (III) and (IV)

C (I), (II) and (IV)

D (I), (II) and (III)

Correct Answer

Option D

Solution

1st I.E. of Be > B In case of Be, electron is removed from 2s orbital which has more penetration power, while in case of B electron is removed from 2p orbital which has less penetration power. 2p electron of B is more shielded from nucleus by the inner electrons than 2s electrons of Be $\therefore$ It is easier to remove 2p electron than 2s electron.