The p-Block Elements Test

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The p-Block Elements Test - 60

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Weekly Quiz Competition

Question 1
1 / -0

Which among the following substances is not a component of the mixture used for glazing pottery?

A
Feldspar

B
Silica

C
Borax

D
Alumina

Solution

Ceramic glaze is an impervious layer or coating of a vitreous substance which has been fused to a ceramic body through firing. Glaze can serve to colour, decorate or waterproof an item.

Pottery glaze is made up of five basic components. These components are silica, alumina, flux, colourants and modifiers.

Hence, option A is correct.
Question 2
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Which of the following does not react with cold water?

A
$$SiC$$

B
$$AIN$$

C
$$CaC_{2}$$

D
$$Al_{4}C_{3}$$

Solution

As $$SiC$$ is a covalent compound, it requires some amount of energy to react with water. So, it doesn't react with cold water.

Option A is correct.
Question 3
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$$Me_3SiCl$$ is mixed with $$Me_2SiCl_2$$ to get a polymers called silicones of the type:

A

B

C
Both A and B

D
None of these
Question 4
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Silica reacts with $$Mg$$ to form a magnesium compound $$A$$. $$A$$ reacts with dilute $$HCl$$ and forms $$B$$. The compound $$B$$ is:

A
$$MgSiO$$

B
$$MgO$$

C
$$Mg{ Cl }_{ 2 }$$

D
$$Si{ Cl }_{ 4 }$$

Solution

It is given that silica reacts with $$Mg$$ to form a magnesium compound $$A$$. $$A$$ reacts with dilute $$HCl$$ to form $$B$$.
The reactions are as follows:
$$2Mg + SiO_2 \rightarrow 2MgO + Si$$
$$MgO + 2HCl \rightarrow MgCl_2 + H_2O$$
Hence, the compound $$B$$ is $$MgCl_2$$.
Question 5
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Borax in its crystal possess:

A
3 tetrahedral unit

B
2 tetrahedral and 2 planar triangular units

C
3 tetrahedral and 2 planar triangular units

D
all tetrahedral units

Solution

Borax $$[Na_2(B_4O_5(OH)_4.8H_2O]$$

$$Sp^2 \to$$ trigonal planar

$$Sp^3 \to$$ tetrahedral

In borax $$2(Sp^2)$$ trigonal planar and $$2(Sp^3)$$ tetrahedral
Question 6
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Microcosmic salt and borax are used in the identification of cations by dry tests. They are respectively :

A
$$Na{ BO }_{ 2 }$$ and $$Na{ PO }_{ 3 }$$

B
$$Na{ NH }_{ 4 }{ HPO }_{ 4 }.{ 4H }_{ 2 }O$$ and $${ Na }_{ 2 }{ B }_{ 4 }{ O }_{ 7 }.10{ H }_{ 2 }O$$

C
$$Na{ PO }_{ 3 }$$ and $$Na{ BO }_{ 2 }$$

D
$${ Na }_{ 2 }{ B }_{ 4 }{ O }_{ 7 }$$ and $$Na{ NH }_{ 4 }{ HPO }_{ 4 }$$

Solution

Microcosmic salt bead test is useful to identify cations like in borax bead test. When the microcosmic salt is heated on platinum wire loop to get sodium meta phosphate,
$$Na(NH_4)HPO_4.4H_2O \rightarrow Na(NH_$)HPO_4 + 4H_2O$$
$$Na(NH_4)HPO_4 \rightarrow NaPO_3 +NH_3 +H_2O$$
(Glass mass)
Now, we have $$NaPO_3$$ which reacts with metallic oxides to give coloured orthophosphates.
Thus, option (B) is the correct answer.
Question 7
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Read the following write-ups and answer the questions at the end of it.
Silicons are synthetic polymers containing repeated $$R_{2}SiO$$ units. Since, the empirical formula is that of a ketone $$(R_{2}CO)$$, the name silicone has been given to these materials. Silicones can be made into oils, rubbery elastomers and resins. They find a variety of applications because of their chemical inertness, water repelling nature, heat- resistance and good electrical insulating property. Commercial silicon polymers are usually methyl derivatives and to a lesser extent phenyl derivatives and are synthesised by the hydrolysis of $$R_{2}SiCl_{2}$$[R=methyl (Me) or phenyl (Ph)]

If we mix $$Me_{3}SiCl$$ with $$Me_{2}SiCl_{2}$$, we get silicones of the type:

A

B

C
both of the above

D
none of the above
Question 8
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One natural source of atmospheric $$CO_2$$ is precipitation reaction such as the precipitation of silicates in the oceans:

$$Mg^{2+}(aq)+SiO_2(dispersed)+2HCO_3(aq)\rightarrow MgSiO_3(s)+2CO_2(g)+H_2O(l)$$

How many grams of magnesium silicate would be precipitated during the formation of $$100$$ L of $$CO_2$$ at $$30^oC$$ and $$775$$ torr?
$$(Mg=24, Si=28, C=12, O=16)$$

A
$$102\ g$$

B
$$410 \ g$$

C
$$205\ g$$

D
$$51\ g$$

Solution

Moles of $$CO_2$$ formed$$=n=\displaystyle\frac{PV}{RT}$$

$$PV=\displaystyle\frac{775}{760} atm\times 100L$$

$$RT=0.0821\ L \ atm$$ $$mol^{-1}$$ $$K^{-1}\times 303K$$

$$n = 4.0992$$

If $$2$$ moles $$CO_2$$ are formed then $$MgSiO_3$$ precipitated is $$1mol$$ and when $$4.0992$$ moles $$CO_2$$ and formed $$MgSiO_3$$ would be $$=\displaystyle\frac{4.0992}{2}$$ $$=2.0496\ mol$$

(molar mass of $$MgSiO_3=100\ g$$ $$mol^{-1}$$

$$=2.0496\times 100 \ g$$
$$=204.96\ g$$ is nothing but $$205\ g$$

Hence, option $$C$$ is correct.
Question 9
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$$Al + N_2 \xrightarrow {\triangle} (A) \xrightarrow {H_2O} (B) \xrightarrow {K_2HgI_4/OH^-} (D)$$ (brown ppt.)

What is $$(D)$$?

A
$$H_2N - Hg - Hg - I$$

B
$$H_2N - Hg - O - Hg - I$$

C
$$H_2N - O -Hg- Hg - I$$

D
$$H_2N - Hg - I - Hg - O$$

Solution

$$Al + N_2 \xrightarrow {\Delta} AlN \xrightarrow {H_2O}NH_3 \xrightarrow {(K_2HgI_4/OH^-)}\, \, \, (D) : H_2N - Hg - O - Hg - I$$ (brown ppt.) (Iodide of Millon's base)
Hence option $$B$$ is correct.
Question 10
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Which is incorrect statement about silicons?

A
They are repeating units $$(SiO_4)$$ in silicates

B
They are synthetic polymers containing repeated $$R_2SiO$$ units

C
They are formed by hydrolysis of $$R_2SiCl_2$$

D
All the above are incorrect statements

Solution

Organic polymers containing silicon in them are called as silicones. These are organosilicon polymers containing $$R_2SiO$$ repeating units and empirical formula analogous to ketone $$(R_2CO)$$. They are formed by hydrolysis of $$R_2SiCl_2$$.