The s-Block Elements Test 27

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The s-Block Elements Test 27

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Weekly Quiz Competition

Question 1
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Lithium borohydride, $$LiB{H}_{4}$$, crystallizes in an orthorhombic system with four molecules per unit cell. The unit cell dimensions are $$a=6.0\mathring { A } ,b=4.4\mathring { A } ,c=7.5\mathring { A } $$. The density of crystals is
$$\left( Li=7,B=11,{ N }_{ A }=6\times { 10 }^{ 23 } \right) $$

A
$$0.74g/{cm}^{3}$$

B
$$1.48g/{cm}^{3}$$

C
$$0.37g/{cm}^{3}$$

D
$$0.90g/{cm}^{3}$$

Solution
Question 2
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Which two processes are involved in the preparation of magnesium sulfate from dilute sulfuric
acid and an excess of magnesium oxide?

A
Neutralisation and filtration

B
Neutralisation and oxidation

C
Thermal decomposition and filtration

D
Thermal decomposition and oxidation

Solution

Metal, metal oxide and metal carbonate reacts with acids to produce salts. When you want magnesium sulfate salts in lab use magnesium oxide and magnesium carbonate to prepare magnesium sulfate salts, because magnesium reacts with sulfuric acids to produce hydrogen gas and that is very dangerous because it explode easily.
so neutralisation and filtration is always need produce magnesium sulfate
Question 3
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The magnitude of property X of five elements from the third period of the Periodic Table, $$P,Q,R,S$$ and $$T$$ is shown $$P,Q,R,S$$ and $$T$$ have cosecutive atomic numbers. The letters do not represent the symbols of the elements.
Which row correctly identifies property X and element R?

A
property X - electrical conductivity ; element R - $$Al$$

B
property X - electronegativity ; element $$R - Si$$

C
property X - melting point ; element $$R - Al$$

D
property X - meltingpoint ; element $$R - Si$$

Solution

Graph
from this we can say that element R is $$Al$$
Question 4
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When dealing with a spillage of metallic sodium it is important that no toxic or flammable products are formed.
Which material should be used if there is a spillage of metallic sodium?

A
Dilute hydrochloric acid

B
Ethanol

C
Sand

D
Water spray

Solution

Sand can be used if there is a spillage of metallic sodium as sand will have no reaction with sodium metal and it serves as a coating to protect sodium from any reaction.
Question 5
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The products obtained on heating $$LiNO_3$$ will be:

A
$$Li_2O + NO_2 +O_2$$

B
$$Li_3N + O_2$$

C
$$Li_2O +NO +O_2$$

D
$$LiNO_3 +O_2$$

Solution

$$LiNO_{3}$$ on heating decomposes to give reddish brown coloured $$NO_{2}$$ gas. $$4LiNO_{3}\rightarrow 2Li_{2}O+4NO_{2}+O_{2}$$.
So option A is correct.
Question 6
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$$KO_2$$ (Potassium superoxide) is used in oxygen cylinders in space and submarine because it:

A
Decomposes to give oxygen

B
Eliminates moisture

C
Absorbs $$CO_2$$

D
Produces ozone
Question 7
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Be and Al exhibit many properties which are similar. But the two elements differ in:

A
forming covalent bonds

B
forming polymeric hydrides

C
exhibiting maximum covalency in compounds

D
exhibiting amphoteric nature in their oxides

Solution

Be and Al shows diagonal resemblance. They only differ in exhibiting maximum covalency in compound.
Question 8
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In which property listed below hydrogen does not resemble alkali metals?

A
Nature of oxide

B
Reducing nature

C
Tendency to form cation

D
Presence of one electron in valence shell

Solution
Question 9
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As compared to alkali metals, alkaline earth metals;

A
are more metallic

B
have higher densities

C
are stronger reducing agents

D
have larger atomic radii

Solution
Question 10
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Alkali metals are characterised by:

A
good conductors of heat and electricity

B
high melting points

C
low oxidation potentials

D
high ionisation potentials

Solution

Alkali metals are good conductors of heat and electricity. Also they have low melting and boiling points. The outermost shell of these metals has 1 electron which is easier to be removed. Hence they have low ionisation energy.

The correct answer is option A.