The s-Block Elements Test 28

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The s-Block Elements Test 28

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Weekly Quiz Competition

Question 1
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The solubility of $$MClO_{4} (M=Li, Na, K, Rb)$$ increases in order of:

A
$$LiClO_{4}< NaClO_{4}< KClO_{4}< RbClO_{4}$$

B
$$NaClO_{4}< RbClO_{4}< LiClO_{4}< KClO_{4}$$

C
$$RbClO_{4}< KClO_{4}< NaClO_{4}< LiClO_{4}$$

D
$$KClO_{4}< LiClO_{4} < NaClO_{4}<RbClO_4$$

Solution

$$LiClO_4$$ is most soluble than others in the 1st group. This is because solubility depends on hydration energy which is size-dependent. As the size increases from top to bottom in a group, hydration energy decreases and solubility also decreases.

The correct order is $$RbClO_4<KClO_4<NaClO_4< LiClO_4.$$
Question 2
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When a standard solution of $$NaOH$$ is left in air for a few hours?

A
a precipitate will form

B
strength will decrease

C
strength will increase

D
the concentration of $$Na^{+}$$ ions will remain constant

Solution
Question 3
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Ease with which hydrides are formed from $$Li$$ to $$Cs$$:

A
decreases

B
increases

C
remains the same

D
none of these

Solution

Due to decrease in reactivity form Li to Cs.
Question 4
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In certain matters, lithium differs other alkali metals, the main reason for this is:

A
small size of lithium atom and $$Li^{+}$$

B
extremely high electropositivity of $$Li$$

C
greater hardness of $$Li$$

D
hydration of $$Li^{+}$$ ion

Solution

In certain matters, lithium differs from other alkali metals(anamalous property); the main reason for this is small size of lithium atom and Li+ and high polarizing power.
Question 5
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Thermal stability of hydrides of first group elements follows the order;

A
$$LiH > NaH > KH > RbH$$

B
$$LiH > KH > NaH> RbH$$

C
$$LiH > RbH > KH > NaH$$

D
$$LiH > KH > RbH > NaH$$

Solution

As we move from top to bottom in a group the size of the alkali metals increases, thereby the bond dissociation energy decreases hence it requires less energy to decompose so thermal stability also decreases.. So the order of thermal stability of IA group elements is
LiH>NaH>KH>RbH
Question 6
1 / -0

Element in the first column of the periodic table are called alkali metals. These metals have:

A
a single valency electron

B
one electron less than an inert gas configuration

C
high melting points

D
high ionisation potentials

Solution

Alkali metals are elements in Group 1 of the periodic table, with the exception of hydrogen. The alkali metals, which include lithium, sodium, potassium, rubidium, caesium, and francium, all have one valence electron and are highly reactive.

Hence the correct answer is option A.
Question 7
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Increasing order of density is:

A
Li < K < Na < Rb < Cs

B
Li < Na < K < Rb < Cs

C
Cs < Rb < K < Na < Li

D
K < Li < Na < Rb < Cs

Solution

Answer A.
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 the atomic size of potassium.
Question 8
1 / -0

The aqueous solutions of lithium salts are poor conductor of electricity rather than other alkali metals because of:

A
high ionisation energy

B
high electronegativity

C
lower ability of $$Li^{+}$$ ions to polarise water molecules

D
higher degree of hydration of $$Li^{+}$$ ions

Solution
Question 9
1 / -0

Which of the following does/do not impart characteristic color to the flame?

A
$$MgSO_4$$

B
$$CaCl_2$$

C
$$Sr(NO_3)_2$$

D
$$BaCl_2$$

Solution
Question 10
1 / -0

Which of the property of alkali metals is not listed correctly?

A
The least electronegative metal: $$Cs$$

B
A natural radioactive metal: $$fr$$

C
The alkali metal with lowest density $$:K$$

D
The most abuntant alkali metal in earth's crust: $$Na$$

Solution

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The s-Block Elements Test 28

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The s-Block Elements Test 28

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Question 1

$$LiClO_{4}< NaClO_{4}< KClO_{4}< RbClO_{4}$$

$$NaClO_{4}< RbClO_{4}< LiClO_{4}< KClO_{4}$$

$$RbClO_{4}< KClO_{4}< NaClO_{4}< LiClO_{4}$$

$$KClO_{4}< LiClO_{4} < NaClO_{4}<RbClO_4$$

Solution

Question 2

a precipitate will form

strength will decrease

strength will increase

the concentration of $$Na^{+}$$ ions will remain constant

Solution

Question 3

decreases

increases

remains the same

none of these

Solution

Question 4

small size of lithium atom and $$Li^{+}$$

extremely high electropositivity of $$Li$$

greater hardness of $$Li$$

hydration of $$Li^{+}$$ ion

Solution

Question 5

$$LiH > NaH > KH > RbH$$

$$LiH > KH > NaH> RbH$$

$$LiH > RbH > KH > NaH$$

$$LiH > KH > RbH > NaH$$

Solution

Question 6

a single valency electron

one electron less than an inert gas configuration

high melting points

high ionisation potentials

Solution

Question 7

Li < K < Na < Rb < Cs

Li < Na < K < Rb < Cs

Cs < Rb < K < Na < Li

K < Li < Na < Rb < Cs

Solution

Question 8

high ionisation energy

high electronegativity

lower ability of $$Li^{+}$$ ions to polarise water molecules

higher degree of hydration of $$Li^{+}$$ ions

Solution

Question 9

$$MgSO_4$$

$$CaCl_2$$

$$Sr(NO_3)_2$$

$$BaCl_2$$

Solution

Question 10

The least electronegative metal: $$Cs$$

A natural radioactive metal: $$fr$$

The alkali metal with lowest density $$:K$$

The most abuntant alkali metal in earth's crust: $$Na$$

Solution

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