The s-Block Elements Test 22

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The s-Block Elements Test 22

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Weekly Quiz Competition

Question 1
1 / -0

Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?

A
$$Li$$

B
$$Na$$

C
$$K$$

D
$$Cs$$

Solution

$$Li$$ reacts with water least vigorously due to the small size and very high hydration energy.
Question 2
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Which of the following is not a similarity of beryllium with aluminium?

A
It becomes passive when treated with conc.$$HNO_3$$.

B
It forms polymeric covalent hydrides.

C
Carbonate of Be is extremely stable.

D
Salts of Be do not impart colour to the flame.
Solution
Beryllium shows resemblance with its diagonally opposite element aluminium.
Points of similarity are-
Both metals have a tendency to form covalent bonds. Eg; Chlorides of both are being covalent are being soluble in organic solvents.
Both $$BeCl_2$$ and $$AlCl_3$$ act as Lewis acids and are used as Friedal Kraft's catalyst.
These two elements have the same electronegativity and polarizing power i.e. charge per radius ration of their ions are very similar.
They form polymeric covalent hydrides.
They become passive when treated with $$conc.HNO_3$$
Salts of Be do not impart colour to the flame.
But, the stability of Carbonate of $$Be$$ is not similar to carbonate of $$Al$$.Hence, option C is the correct answer.
Question 3
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Dehydration of hydrates of halides of calcium, barium and strontium i.e., $$CaCl_2.6H_2O,BaCl_2.2H_2O,SrCl_2.2H_2O$$ can be achieved by heating. These become wet on keeping in the air. Which of the following statements is correct about these halides?

A
The act as dehydrating agents.

B
They can absorb moisture from air.

C
They have tendency to from hydrate which decreases from calcium to barium.

D
All of the above

Solution

Halides of calcium, barium and strontium act as dehydrating agent as they are hygroscopic in nature. They absorb moisture. Also they have tendency to form hydrate which decreases from $$Ca^{2+}$$ to $$Sr^{2+}$$ due to increase in size and decrease in polarization power.
Question 4
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Metal carbonates decompose on heating to give metal oxide and carbon dioxide. Which of the metal carbonates is most stable thermally?

A
$$MgCO_3$$

B
$$CaCO_3$$

C
$$SrCO_3$$

D
$$BaCO_3$$

Solution

$$BaCO_3$$ is most thermally stable as the size of $$Ba^{2+}$$ is big due to which it is having low polarising power and thus cannot polarize oxygen electrons due to which carbonates of large cations are stable.
Question 5
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$${Be}_{2}C+4{H}_{2}O\longrightarrow 2X+{CH}_{4}$$
$$X+2OH\longrightarrow Y$$
(X) and (Y) formed in the above two reactions are :

A
$${BeCO}_{3}$$ and $$Be\left(OH\right)_{2}$$ respectively

B
$$Be\left(OH\right)_{2}$$ and $${BeCl}_{2}$$ respectively

C
$$Be\left(OH\right)_{2}$$ and $$\left[Be\left(OH\right)_{4}\right]^{2-}$$ respectively

D
$$\left[Be\left(OH\right)_{4}\right]^{2-}$$ and $${BeCl}_{2}$$ respectively

Solution

The reaction involved are-
$$Be_2C+4H_2O \rightarrow 2Be(OH)_2 +CH_4$$
Hence X is $$Be(OH)_2$$
Now,
$$Be(OH)_2 +2OH^{-} \rightarrow [Be(OH)_4]^{2-}$$
So, Y is $$[Be(OH)_4]^{2-}$$
Question 6
1 / -0

The solubility of metal halides depends on their nature, lattice enthalpy and hydration enthalpy of the individual ions. Amongst fluorides of alkali metals, the lowest solubility of LiF in water is due to:

A
ionic nature of lithium fluoride

B
high lattice enthalpy

C
high hydration enthalpy for lithium ion

D
low ionisation enthalpy of lithium atom

Solution

Lowest solubility of $$LiF$$ is due to high lattice enthalpy which is higher than hydration enthalpy. Hence, the dissociation of $$Li-F$$ bond becomes difficult.
Question 7
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When $$LiNO_{3}$$ is heated, it gives oxide, $$Li_{2}O$$, whereas other alkali metal nitrates decompose to give corresponding :

A
nitrite

B
peroxide

C
both nitrite and oxide

D
none of these

Solution

Due to the small size of $$Li^{+}$$, it is very polarizing and favours the formation of $$LiO_2$$.
$$4LiO_3 \rightarrow 2Li_2O + 4NO_2 + O_2$$
While other alkali metal nitrates decomposes to give corresponding nitrite.
$$NaN{O}_{3} \xrightarrow{\Delta} NaN{O}_{2} + \cfrac{1}{2} {O}_{2}$$
Question 8
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The main constituents of pearl are:

A
ammonium sulphate and sodium carbonate

B
aragonite are conchiolin

C
calcium carbonate and magnesium carbonate

D
calcium oxide and ammonium chloride

Solution

The chief component of the nacre that constitutes the pearl is aragonite $$(CaCO_3)$$. Nacre also contains a small amount of conchiolin, a hornlike organic substance (albuminoid) that is the main constituent of the mollusk's outer shell.
Question 9
1 / -0

Amphoteric hydroxides react with both alkalies and acids. Which of the following Group 2 metal hydroxides is soluble in sodium hydroxides?

A
$$Be(OH)_2$$

B
$$Mg(OH)_2$$

C
$$Ca(OH)_2$$

D
$$Ba(OH)_2$$

Solution

Beryllium bydroxide, $$Be(OH)_2$$ is amphoteric in nature, as it reacts with acid and alkali both.
$$Be(OH)_2 + 2HCl \rightarrow BeCl_2 + 2H_2O$$
$$Be(OH)_2 + 2NaOH \rightarrow Na_2BeO_2 + 2H_2O$$
Question 10
1 / -0

Which of the following is used as a sources of hydrogen for filling of balloons that is convenient and can be carried around?

A
Lithium hydride

B
Sodium borohydride

C
Calcium metal

D
Sodium formate
Solution
- LiH is produced by treating lithium metal with hydrogen gas.
- It is used for filling meteorological balloons which carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde
Hence option A is correct answer.

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Re-Attempt Weekly Quiz Competition

The s-Block Elements Test 22

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The s-Block Elements Test 22

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Question 1

$$Li$$

$$Na$$

$$K$$

$$Cs$$

Solution

Question 2

It becomes passive when treated with conc.$$HNO_3$$.

It forms polymeric covalent hydrides.

Carbonate of Be is extremely stable.

Salts of Be do not impart colour to the flame.

Solution

Question 3

The act as dehydrating agents.

They can absorb moisture from air.

They have tendency to from hydrate which decreases from calcium to barium.

All of the above

Solution

Question 4

$$MgCO_3$$

$$CaCO_3$$

$$SrCO_3$$

$$BaCO_3$$

Solution

Question 5

$${BeCO}_{3}$$ and $$Be\left(OH\right)_{2}$$ respectively

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

$$Be\left(OH\right)_{2}$$ and $$\left[Be\left(OH\right)_{4}\right]^{2-}$$ respectively

$$\left[Be\left(OH\right)_{4}\right]^{2-}$$ and $${BeCl}_{2}$$ respectively

Solution

Question 6

ionic nature of lithium fluoride

high lattice enthalpy

high hydration enthalpy for lithium ion

low ionisation enthalpy of lithium atom

Solution

Question 7

nitrite

peroxide

both nitrite and oxide

none of these

Solution

Question 8

ammonium sulphate and sodium carbonate

aragonite are conchiolin

calcium carbonate and magnesium carbonate

calcium oxide and ammonium chloride

Solution

Question 9

$$Be(OH)_2$$

$$Mg(OH)_2$$

$$Ca(OH)_2$$

$$Ba(OH)_2$$

Solution

Question 10

Lithium hydride

Sodium borohydride

Calcium metal

Sodium formate

Solution

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