The s-Block Elements Test 20

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The s-Block Elements Test 20

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Weekly Quiz Competition

Question 1
1 / -0

Which one of the following will not give flame test?

A
$$Ca$$

B
$$Ba$$

C
$$Sr$$

D
$$Be$$
Question 2
1 / -0

The increasing order of the density of alkali metals :

A
Li < K < Na < Rb < Cs

B
Li < Na < K < Rb < Cs

C
Cs < Rb < Na < K < Li

D
Cs < Rb < K < Na < Li

E
Li < Na < Rb < K < Cs

Solution

Due to their large size, the atoms of alkali metals are less closely packed.

Consequently, have low density.

On going down the group, both the atomic size and atomic mass increase but the increase in atomic mass compensates the bigger atomic size.

As a result, the density of alkali metals increases from Li to Cs.

Potassium is, however, lighter than sodium. It is probably due to an unusual increase in atomic size of potassium.

Hence the correct option is A.
Question 3
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Which of the following alkali metals when burnt in air forms a mixture of oxide as well as nitride?

A
K

B
Na

C
Li

D
Cs

Solution

The alkali metals tarnish in dry air due to the formation of their oxides which in turn react with moisture to form hydroxides. They burn vigorously in oxygen forming oxides. Lithium forms monoxide $${Li}_{2}O$$, sodium forms peroxide $${Na}_{2}{O}_{2}$$, the other metals form superoxides $${O}^{2-}$$ ions.
$$4Li+{ O }_{ 2 }\rightarrow 2{ Li }_{ 2 }O$$ (normal oxide)
$$2Na+{ O }_{ 2 }\rightarrow 2{ Na }_{ 2 }{O}_{2}$$ (peroxide)
$$M+{ O }_{ 2 }\rightarrow { M }{ O }_{2}$$ (superoxide)
where M is $$M=K,Rb,Cs$$
In all these oxides the oxidation state of the alkali metal is +1. Lithium shows exceptional behaviour in reacting directly with nitrogen of air to form the nitride, $${ Li}_{ 3 }N$$ .
Question 4
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The first element of the groups 1 and 2 are different from other members of the respective groups. Their behaviour is more similar to the second element of the following groups. What is this relationship known as?

A
Anomalous relationship

B
Periodic relationship

C
Diagonal relationship

D
Chemical relationship

Solution

The similarities (in many of properties) between first element of a group and second element of the next group is called diagonal relationship.
Thus, Li ( first element of group 1) shows diagonal relationship with Mg (second element of group 2).
Also, Be ( first element of group 2) shows diagonal relationship with Al (second element of group 13).
Also, B ( first element of group 13) shows diagonal relationship with Si (second element of group 14).
Question 5
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The pair of amphoteric oxides is:

A
$$BeO, ZnO$$

B
$$Al_2O_3,Li_2O$$

C
$$BeO, BO_3$$

D
$$BeO, MgO$$

Solution

$$BeO$$ and $$ZnO$$ are amphoteric in nature because they can react both in acidic as well as a basic solution.
Here $$M = Be,\ Zn$$
Reaction with acids:
$$ MO\quad +\quad 2{ H }^{ + }\quad \rightarrow \quad { M }^{ 2+ }\quad +\quad { H }_{ 2 }O $$
Reaction with base:
$$ MO\quad +\quad { H }_{ 2 }O\quad +\quad 2O{ H }^{ - }\quad \rightarrow \quad { [M{ (OH) }_{ 4 }] }^{ 2- } $$
Question 6
1 / -0

Lithium salts are mostly hydrated like $$ LiCl.2H_2O $$ due to:

A
maximum ionisation enthalpy

B
maximum degree of hydration of $$Li^+$$

C
maximum hydroscopic nature

D
maximum chemical reactivity.

Solution

$$ { Li }^{ + } $$ ion being small in size is surrounded by large no. of water molecules on account of which it has very hydration energy. Hence, it is heavily hydrated and have high degree of hydration.
Question 7
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Directions For Questions

Beryllium differs from reset of the alkaline earth metals on account of its small size, and high electronegativity as compared to other alkaline earth metals. However it shows diagonal relationship with aluminium of the next period. Due to high polarising power of $$Be^{2+}$$ and $$Al^{3+}$$ their compounds develop covalent nature.

...view full instructions

Which of the following is not the point of difference between Be and other alkaline earth metals?

A
It has a tendency to form covalent bonds.

B
It dissolves in alkalies with evolution of hydrogen.

C
Its oxides and hydroxides are amphoteric.

D
Its carbide gives acetylene on hydrolysis

Solution

$$Be_2C$$ gives methane on hydrolysis while other carbides give acetylene.

$$Be_2C + 4H_2O \rightarrow 3 2Be(OH)_2 + CH_4$$
Question 8
1 / -0

Which nitrate will decompose to give $$NO_2$$ on heating?

A
$$NaNO_3$$

B
$$KNO_3$$

C
$$RbNO_3$$

D
$$LiNO_3$$

Solution

Only $$LiNO_3$$ gives $$NO_2$$ on heating. All other nitrates give oxygen.
$$4LiNO_3 \, \xrightarrow{\Delta} \, 2Li_2O \, + \, 4NO_2 \, + \, O_2.$$
$$2NaNO_3 \, \xrightarrow{\Delta} \, 2NaNO_2 \, + \, O_2$$
Question 9
1 / -0

Which is the correct sequence of solubility of carbonates of alkaline earth metals?

A
$$BaCO_3 > SrCO_3 > CaCO_3 > MgCO_3$$

B
$$MgCO_3 > CaCO_3 > SrCO_3 > BaCO_3$$

C
$$CaCO_3 > BaCO_3 > SrCO_3 > MgCO_3$$

D
$$BaCO_3 > CaCO_3 > SrCO_3 > MgCO_3$$

Solution

Solubility of carbonates decreases on moving down the group as hydration energy decreases.
Question 10
1 / -0

Which of the following does not show diagonal relationship between beryllium and aluminium?

A
Both $$BeO$$ and $$Al_2O_3$$ are amphoteric in nature.

B
Both beryllium and aluminium form polymetric covalent hydrdes.

C
Both beryllium and aluminium form nitrides with nitrogen which evolve $$NH_3$$ with water.

D
Both metal carbonates are highly stable.

Solution

$$Be$$ and $$Al$$ show diagonal relation but both of their carbonates are unstable because smaller and more charged metal cations tend to distort the electron cloud of $$CO_3^{2+} $$ ions (polarization).

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The s-Block Elements Test 20

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The s-Block Elements Test 20

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Question 1

$$Ca$$

$$Ba$$

$$Sr$$

$$Be$$

Question 2

Li < K < Na < Rb < Cs

Li < Na < K < Rb < Cs

Cs < Rb < Na < K < Li

Cs < Rb < K < Na < Li

Li < Na < Rb < K < Cs

Solution

Question 3

K

Na

Li

Cs

Solution

Question 4

Anomalous relationship

Periodic relationship

Diagonal relationship

Chemical relationship

Solution

Question 5

$$BeO, ZnO$$

$$Al_2O_3,Li_2O$$

$$BeO, BO_3$$

$$BeO, MgO$$

Solution

Question 6

maximum ionisation enthalpy

maximum degree of hydration of $$Li^+$$

maximum hydroscopic nature

maximum chemical reactivity.

Solution

Question 7

It has a tendency to form covalent bonds.

It dissolves in alkalies with evolution of hydrogen.

Its oxides and hydroxides are amphoteric.

Its carbide gives acetylene on hydrolysis

Solution

Question 8

$$NaNO_3$$

$$KNO_3$$

$$RbNO_3$$

$$LiNO_3$$

Solution

Question 9

$$BaCO_3 > SrCO_3 > CaCO_3 > MgCO_3$$

$$MgCO_3 > CaCO_3 > SrCO_3 > BaCO_3$$

$$CaCO_3 > BaCO_3 > SrCO_3 > MgCO_3$$

$$BaCO_3 > CaCO_3 > SrCO_3 > MgCO_3$$

Solution

Question 10

Both $$BeO$$ and $$Al_2O_3$$ are amphoteric in nature.

Both beryllium and aluminium form polymetric covalent hydrdes.

Both beryllium and aluminium form nitrides with nitrogen which evolve $$NH_3$$ with water.

Both metal carbonates are highly stable.

Solution

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