The s-Block Elements Test 48

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The s-Block Elements Test 48

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Weekly Quiz Competition

Question 1
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Which of the following statement(s) is/are INCORRECT ?

A
Generally the radius trend and the ionization energy trend across a period are opposite.

B
Metallic and covalent radii of potassium are 2.3 $$A ^0$$and 2.03 $$A^0$$ respectively.

C
Amongst $$ Li^{-}$$, $$ B^{-}$$ and $$ C^{-}$$, $$ Li^{-}$$ is least stable ion

D
Atomic and ionic radii of Niobium and Tantalum are almost same.

Solution

(A) Across the period ,size decreases as electrons are added in the same shell and nuclear charge increases by one unit for addition of each successive element.

In contrary ,the ionization energy increases as size of atom decreases and nuclear charge increases.

(B) $$r_{metalic}> r_{covalent}$$ (covalent bond formation involves the overlapping of orbitals.

(C) $$^{_{3}^\textrm{}}Li^{-}$$ -$$1s^{2}2s^{2}$$ completely filled stable configuration ,so more stable.
$$_{4}^\textrm{}Be^{-}$$ - $$1s^{2}2s^{2}2p^{1}$$
$$_{5}\textrm{}B^{-}$$ -$$1s^{2}2s^{2}2p^{2}$$
$$_{6}^\textrm{}C^{-}$$-$$1s^{2}2s^{2}2p^{3}$$ half filled stable configuration ,so more stable.

Option C is correct.
Question 2
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A metal $$M$$ readily forms water soluble sulphate and water insoluble hydroxide, $$M(OH)_2$$. Its oxide $$MO$$ is amphoteric, hard and having high melting point. The alkaline earth metal is :

A
$$Mg$$

B
$$Ca$$

C
$$Be$$

D
$$Ba$$
Solution
Beryllium forms Beryllium sulfate $$(BeSO_4)$$ which is water-soluble.
Beryllium forms Beryllium hydroxide $$(Be(OH)_2)$$ which is water-insoluble.
Beryllium forms Beryllium oxide $$(BeO)$$ which is amphoteric, hard, and having high melting point.
Question 3
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The ion having maximum value of hydration energy is:

A
$$Li^+$$

B
$$Na^+$$

C
$$K^+$$

D
$$Cs^+$$

Solution
Question 4
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Sodium metal cannot be stored under

A
benzene

B
kerosene

C
alcohol

D
toluene

Solution

Sodium metal cannot be stored under alcohol because it reacts with alcohol to form sodium alkoxide and hydrogen gas.

$$2C_2H_5OH +2Na \rightarrow 2C_2H_5ONa+H_2$$
Question 5
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If $$Na$$ is heated in presence of air, it forms

A
$$Na_2CO_3$$

B
$$Na_2O_2$$

C
$$Na_2O$$

D
Both $$ (B)$$ and $$(C)$$

Solution

When Na is heated in the presence of air or oxygen, Na burns to form sodium oxide and sodium peroxide.

$$6Na+2O_2\to 2Na_2O+Na_2O_2$$
Question 6
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Point out of the incorrect statements regarding $$Be$$ (Group $$IIA$$)

A
It forms an ionic carbide

B
Its carbonates decomposes on heating

C
Its halides are covalent

D
It is easily attacked by water

Solution

$$Be$$ does not react easily with normal water. Beryllium reacts with water to produce oxide beryllium, beryllium hydroxide and hydrogen. The reaction takes place in a boiling solution.

$$2Be + 3H_2O \to BeO + Be(OH)_2 + 2H_2$$
Question 7
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Directions For Questions

Beryllium shows different properties from rest of the alkaline earth metals because of its small atomic and ionic size, high electronegativity and high polarising power. But beryllium shows similarities in properties to the second member of the next group i.e. aluminium on account of similar atomic and ionic size and nearly same polarising power.

...view full instructions

Which of the following statements is true?

A
$$BeO$$ and $$Be\left(OH\right)_{2}$$ both are purely basic in nature.

B
$$Be$$ can expand its covalency to six.

C
$$Be$$ largely forms covalent compounds which get easily hydrolysed.

D
$$Be$$ combines with hydrogen upon heating to form $$BeH_{2}$$

Solution

(A) $$BeO$$ and $$Be\left(OH\right)_{2}$$ are amphoteric in nature.
(B) $$Be$$ cannot expand its covalency greater than four as it does not have vacant d-orbitaks.
(C) Correct statement; on account of high ionisation enthalpy and small size.
(D) Do not combine directly with $${H}_{2}$$ on heating to form hydride.
Method used is: $$2BeCl_{2}+LiAlH_{4}\longrightarrow2BeH_{2}+LiCl+AlCl_{3}$$
Question 8
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Which of the following has maximum solubility in water?

A
NaCl

B
KCl

C
RbCl

D
LiCl

Solution

As we go down group $$\mathrm{I}$$, solobulity of chlorides increases.
So, RbCl has the maximum solubility in water.
Hence, Option "C" is the correct answer.
Question 9
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The atomic radii of alkali metals $$(M)$$ lie in the order $$Li < Na < K < Rb$$ but the radii of $$M^{+}$$ ions in aqueous solution lie in the reverse order $$Li^{+} > Na^{+} > K^{+} > Rb^{+}$$. What is the reason for this reverse order (on going from $$Li$$ to $$Rb$$)?

A
Gradual increase in ionisation energy

B
Increasing weakness of the metallic bond

C
Increasing electropostive character

D
Decreasing degree of hydration

Solution

Higher the charge density more is the hydration. The charge density of Li ion is highest so its size of hydrated ion will be largest.
Question 10
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Directions For Questions

Beryllium shows different properties from rest of the alkaline earth metals because of its small atomic and ionic size, high electronegativity and high polarising power. But beryllium shows similarities in properties to the second member of the next group i.e. aluminium on account of similar atomic and ionic size and nearly same polarising power.

...view full instructions

Which amongst the following is soluble in water?

A
$$BeSO_{4}$$

B
$$BeO$$

C
$$Be\left(OH\right)_{2}$$

D
$$BeCl_{2}$$

Solution

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The s-Block Elements Test 48

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Question 1

Generally the radius trend and the ionization energy trend across a period are opposite.

Metallic and covalent radii of potassium are 2.3 $$A ^0$$and 2.03 $$A^0$$ respectively.

Amongst $$ Li^{-}$$, $$ B^{-}$$ and $$ C^{-}$$, $$ Li^{-}$$ is least stable ion

Atomic and ionic radii of Niobium and Tantalum are almost same.

Solution

Question 2

$$Mg$$

$$Ca$$

$$Be$$

$$Ba$$

Solution

Question 3

$$Li^+$$

$$Na^+$$

$$K^+$$

$$Cs^+$$

Solution

Question 4

benzene

kerosene

alcohol

toluene

Solution

Question 5

$$Na_2CO_3$$

$$Na_2O_2$$

$$Na_2O$$

Both $$ (B)$$ and $$(C)$$

Solution

Question 6

It forms an ionic carbide

Its carbonates decomposes on heating

Its halides are covalent

It is easily attacked by water

Solution

Question 7

$$BeO$$ and $$Be\left(OH\right)_{2}$$ both are purely basic in nature.

$$Be$$ can expand its covalency to six.

$$Be$$ largely forms covalent compounds which get easily hydrolysed.

$$Be$$ combines with hydrogen upon heating to form $$BeH_{2}$$

Solution

Question 8

NaCl

KCl

RbCl

LiCl

Solution

Question 9

Gradual increase in ionisation energy

Increasing weakness of the metallic bond

Increasing electropostive character

Decreasing degree of hydration

Solution

Question 10

$$BeSO_{4}$$

$$BeO$$

$$Be\left(OH\right)_{2}$$

$$BeCl_{2}$$

Solution

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