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CBSE Questions for Class 11 Medical Chemistry The S-Block Elements Quiz 9 - MCQExams.com
CBSE
Class 11 Medical Chemistry
The S-Block Elements
Quiz 9
The products obtained on heating $$LiNO_3$$ will be:
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$$Li_2O + NO_2 +O_2$$
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$$Li_3N + O_2$$
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$$Li_2O +NO +O_2$$
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$$LiNO_3 +O_2$$
Explanation
$$LiNO_{3}$$ 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.
Select the correct statements :
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Solubility of alkali earth metal's oxide decreases down the group
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Solubility of alkaline earth metal's sulphide increases down the group
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Solubility of alkali metal's hydroxide increases down the group
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Solubility of alkali metal's fluorides increases down the group
Be and Al exhibit many properties which are similar. But the two elements differ in:
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forming covalent bonds
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forming polymeric hydrides
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exhibiting maximum covalency in compounds
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exhibiting amphoteric nature in their oxides
Explanation
Be and Al shows diagonal resemblance. They only differ in exhibiting maximum covalency in compound.
The softness of group IA metals increases down the group with increasing atomic number.
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True
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False
Explanation
The extent of metallic bonding decreases with the increase in atomic size down the group. In other words, close-packing of atoms in crystal lattice decreases from Li to Cs, thereby resulting in an increased softness.
The softness of group IA metals increases down the group with increasing atomic number. This is a true statement.
In which property listed below hydrogen does not resemble alkali metals?
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Nature of oxide
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Reducing nature
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Tendency to form cation
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Presence of one electron in valence shell
As compared to alkali metals, alkaline earth metals;
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are more metallic
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have higher densities
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are stronger reducing agents
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have larger atomic radii
When a standard solution of $$NaOH$$ is left in air for a few hours?
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a precipitate will form
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strength will decrease
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strength will increase
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the concentration of $$Na^{+}$$ ions will remain constant
Ease with which hydrides are formed from $$Li$$ to $$Cs$$:
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decreases
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increases
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remains the same
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none of these
Explanation
Due to decrease in reactivity form Li to Cs.
In certain matters, lithium differs other alkali metals, the main reason for this is:
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small size of lithium atom and $$Li^{+}$$
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extremely high electropositivity of $$Li$$
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greater hardness of $$Li$$
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hydration of $$Li^{+}$$ ion
Explanation
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.
Alkali metals are characterised by:
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good conductors of heat and electricity
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high melting points
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low oxidation potentials
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high ionisation potentials
Explanation
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.
Thermal stability of hydrides of first group elements follows the order;
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$$LiH > NaH > KH > RbH$$
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$$LiH > KH > NaH> RbH$$
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$$LiH > RbH > KH > NaH$$
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$$LiH > KH > RbH > NaH$$
Explanation
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
Element in the first column of the periodic table are called alkali metals. These metals have:
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a single valency electron
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one electron less than an inert gas configuration
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high melting points
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high ionisation potentials
Explanation
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.
The solubility of $$MClO_{4} (M=Li, Na, K, Rb)$$ increases in order of:
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$$LiClO_{4}< NaClO_{4}< KClO_{4}< RbClO_{4}$$
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$$NaClO_{4}< RbClO_{4}< LiClO_{4}< KClO_{4}$$
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$$RbClO_{4}< KClO_{4}< NaClO_{4}< LiClO_{4}$$
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$$KClO_{4}< LiClO_{4} < NaClO_{4}<RbClO_4$$
Explanation
$$LiClO_4$$ 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 $$RbClO_4<KClO_4<NaClO_4< LiClO_4.$$
Increasing order of density is:
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Li < K < Na < Rb < Cs
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Li < Na < K < Rb < Cs
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Cs < Rb < K < Na < Li
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K < Li < Na < Rb < Cs
Explanation
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.
The aqueous solutions of lithium salts are poor conductor of electricity rather than other alkali metals because of:
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high ionisation energy
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high electronegativity
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lower ability of $$Li^{+}$$ ions to polarise water molecules
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higher degree of hydration of $$Li^{+}$$ ions
Which of the following does/do not impart characteristic color to the flame?
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$$MgSO_4$$
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$$CaCl_2$$
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$$Sr(NO_3)_2$$
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$$BaCl_2$$
Which of the property of alkali metals is not listed correctly?
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The least electronegative metal: $$Cs$$
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A natural radioactive metal: $$fr$$
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The alkali metal with lowest density $$:K$$
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The most abuntant alkali metal in earth's crust: $$Na$$
The alkali metals
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form slat like hydrides
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posses low ionisation potential values
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have low density
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have high affinity for non-metals
Correct order of polarising power is
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$$Cs^+ < K^+ < Mg^{2+} < Al^{3+}$$
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$$K^+ < Cs^+ < Mg^{2+} < Al^{3+}$$
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$$Cs^+ < K^+ < Al^{3+} < Mg^{2+}$$
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$$K^+ < Cs^+ < Al^{3+} < Mg^{2+}$$
Explanation
According to Fajan's rule polarising power depends on size of cation and charge on cation.More the charge on cation and smaller the size of cation will leads to high polarising power.
so correct order is$$ Cs^{+} < K^{+} < Mg^{2+} < Al^{3+}$$
The ionic radii of $$Li^{+}, Na^{+}, K^{+}$$ are in which of the following order
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$$K^{+} > Na^{+} > Li^{+}$$
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$$K^{+} > Na^{+} < Li^{+}$$
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$$K^{+} < Na^{+} < Li^{+}$$
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$$Li^{+} > Na^{+} < K^{+}$$
Explanation
As we move down the group number of shell increases and hence radii increases.
So correct order is
$$K^{+} > Na^{+} > Li^{+}$$
Arrange the following in increasing order of their atomic radius $$Na, K, Mg, Rb$$
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$$Mg < K < Na < Rb$$
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$$Mg < Na < K < Rb$$
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$$Mg < Na < Rb < K$$
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$$Na < K < Rb < Mg$$
Explanation
Across a period from left to right atomic radius decreases and down the group atomic radius increases.
So correct order is: $$Mg < Na < K < Rb$$
Property of the alkali metals that increases with their atomic number is:
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Ionic mobility of their ions in water.
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Solubility of their sulphates
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Solubility of their carbonates
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Solubility of their hydroxides
Explanation
As size of cation increases, the size of hydrated ions in water decreases and thus ionic mobility increases.
Diagonal relationship is shown by
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Elements of first period
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Elements of second period
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Elements of third period
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(b) and (c) both
Explanation
Coorect option is D.
In which of the following groups all the three members are of the alkaline earth metals family
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$$Al_, Sr, Ti$$
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$$Li, Na, K$$
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$$Mg, Ba, Ca$$
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$$Rb, Cs, Fr$$
Explanation
$$Mg, Ba$$ and $$Ca$$ belongs to alkaline earth metals family.
Lithium shows diagonal relationship with
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$$Al$$
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$$Mg$$
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$$Pb$$
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$$Hg$$
Explanation
Lithium shows diagonal resemblance with aluminium due to similar charge to size ratio.
Which of the following alkali metals is smallest in size?
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$$Rb$$
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$$K$$
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$$Na$$
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$$Li$$
Explanation
$$Li$$ is smallest in size among the alkali metals as it has minimum number of shells.
Cause of diagonal relationship is
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Similar electronic configuration of the elements
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Similar $$e/r$$ ratio of the elements
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Similar number of valency electrons in the elements
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Same atomic weights of the electrons
Explanation
Diagonal resemblance is due to similar charge to size ratio (i.e. $$e/r\ ratio$$).
Potassium is kept in
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Alcohol
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Water
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Kerosene
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Liquid ammonia
Explanation
Alkali metals are highly reactive metals. They react with
Alcohol - $$2C_2H_5OH+2K \rightarrow 2C_2H_5OK+H_2$$
Water - $$2K+2H_2O \rightarrow 2KOH+H_2$$
Ammonia - $$K+(x+y)NH_3 \rightarrow \underset {Ammoniated \ cation}{[K(NH_3)_x]^+ }+ \underset {Ammoniated \ electron}{[e(NH_3)_y]^-}$$
But they do not react with kerosene.
Alkali metals lose electrons in
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$$ s-$$ orbitals
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$$ p-$$ orbitals
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$$ d-$$ orbitals
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$$ f-$$ orbitals
Explanation
Alkali metals lose electrons in $$ s-$$ orbital because their valence electrons are present in $$ s-$$ orbitals.
Alkali metals in each period have
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Smallest size
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Lowest ionization potential
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Highest ionization potential
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Highest electronegativity
Explanation
Alkali metals have lowest ionization potential in each period.
Aluminium is diagonally related to ( in periodic table )
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$$Li$$
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$$C$$
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$$B$$
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$$Be$$
Explanation
Aluminium is diagonally related to beryllium ($$Be$$).
Which of the following statement is correct regarding alkali metals?
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Cation is less stable than the atom
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Cation is smaller than the atom
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Size of cation and atom is the same
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Cation is greater in size than the atom
Explanation
After removal of an electron the effective nuclear charge per electron increases hence the size decreases.
Which of the following show diagonal relationship
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$$B$$ and $$Si$$
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$$B$$ and $$Al$$
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$$B$$ and $$Ga$$
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$$B$$ and $$C$$
Explanation
$$B$$ shows diagonal relationship with $$Si$$.
Beryllium differs from rest of the members of its family (Group $$IIA$$) in many ways. The reason for this is its
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Small size and higher electronegativity
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Small size and lower electronegativity
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Large size and lower ionisation energy
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Large size and larger ionic radius
Explanation
Beryllium differs from the rest of the members of its family (Group $$IIA$$) in many ways. The reason for this is due to its:
(i) small atomic size.
(ii) high electronegativity.
(iii) absence of $$d$$ orbitals.
$$Li$$ shows the diagonal relationship with
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$$Mg$$
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$$B$$
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$$Al$$
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$$C$$
Explanation
Elements of $$2^{nd}$$ period often show resemblance to the element of the $$3^{rd}$$ period diagonaly placed to it. This type of behaviour is called as digonal relationship. $$Li$$ shows the diagonal relationship with $$Mg$$.
Which of the following is a false statement?
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Fluorine is more electronegative than chlorine
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Nitrogen has greater $$IE_1$$ than oxygen
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Lithium is amphoteric
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Chlorine is an oxidising agent
Explanation
Lithium is basic in nature and hence it is not amphoteric. All the other statements are correct.
Electronegative beryllium is approximately equal to that of
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Aluminium
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Boron
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Magnesium
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Sodium
Explanation
Element - $$Be\ \ \ \ Al$$
Electronegative - $$1.5\ \ \ \ 1.5$$
Be has a diagonal relationship with Al.
Rare-earth elements are exhibited by
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At. no. 58 to 71
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At. no.21 to 30
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At. no. 39 to 71
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At. no. 81 to 91
Explanation
Atomic number 58 to 71 are rare earth metals and is called Lanthanoid series.
Which alkali metal is most metallic in character?
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$$K$$
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$$Cs$$
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$$Na$$
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$$Li$$
Explanation
$$Cs > Rb > K > Na > Li$$ -- Metallic character decreasing order.
Note: Down the group metallic character increases.
With the increase in atomic weights, melting points of the alkali metals
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Increase
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Decrease
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Remain constant
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Do not show definite trend
Explanation
With increase in atomic mass, melting points of alkali metals decreases due to increase in kernel size and decrease in strength of metallic bond.
The most electropositive amongst the alkaline earth metal is
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Beryllium
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Magnesium
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Calcium
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Barium
Explanation
As we go down group electropositive character increases because $$I.E.$$ decreases.
$$Ba$$ is the most electropositive element in the group.
The alkali metals are low melting. Which of the following alkali metals is expected to melt if the room temperature rises to $$30^o$$?
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Na
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K
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Rb
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Cs
Explanation
The melting point decreases down the group because the size increases and the forces in metallic bonding decreases. Melting point Cs = 302K.
Which of the following elements would lose an electron easily?
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Mg
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Na
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K
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Ca
Explanation
Na and K belong to the same group. i.e. Group I. Ca and Mg belong to the Group II. As we go down in a group, it is easier to remove the electron from the outermost shell. K has one electron in outermost shell and has lowest ionisation energy so it can lose electron most easily.
In the following ions:
$$Mn^{3+}$$, $$V^{3+}$$, $$Cr^{3+}$$, $$Ti^{3+}$$
(Atomic no. : $$Mn = 25$$, $$V = 23$$, $$Cr = 24$$, $$Ti = 22$$)
Which ion has the highest number of unpaired electrons?
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$$Mn^{3+}$$
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$$V^{3+}$$
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$$Cr^{3+}$$
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$$Ti^{3+}$$
Explanation
$$Mn^{3+} (3d^{4}4s^{0})$$. It has $$4$$ unpaired electrons.
Which of the following is the outermost shell for elements of period 2?
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K shell
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L shell
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M shell
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N shell
Explanation
In period 2, there are 2 shells, i.e. K and L.
Which of the following metal has lowest melting point?
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$$ Na $$
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$$ K $$
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$$ Rb $$
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$$Cs $$
Explanation
Cesium has lowest melting point.
The properties of lithium are similar to those of Mg.
This is because
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both have nearly the same size
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the ratio of their charge to size is nearly the same
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both have similar electronic configurations
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both are found together in nature.
Explanation
Answer is option (B)
$$Lithium$$ shows diagonal relationship with $$magnesium$$ since they have almost the same polarizing power i.e., charge/size ratio.
Match List-I with List-II and select the correct answer using the codes given below the lists:
(A) $$BaSO_{4} + ZnS$$ (1) Explosive
(B) $$NI_{3}$$ (2) Oxidiser in rocket propellants
(C) $$N_{2}O_{4}$$ (3) Space capsule
(D) $$KO_{2}$$ (4) Pigment
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$$A - 3, B - 1, C - 4, D - 2$$
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$$A - 4, B - 1, C - 2, D - 3$$
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$$A - 3, B - 4, C - 1, D - 2$$
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$$A - 4, B - 3, C - 2, D - 1$$
Explanation
$$BaSO_4 + ZnS$$ this show pigment type of reaction
$$NI_3$$ show the explosive type of reaction
$$N_2O_4$$ show oxidiser in rocket propellsnts
$$KO_2$$ is show in Space capsule
hence B is correct answer
Metal(s) M in the following equation is/are
$$M + N_{2} \overset{\Delta}{\rightarrow}$$ Metal nitride
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$$Na$$
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$$Li$$
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$$Cs$$
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$$Mg$$
Explanation
M containing two metal one is Li and another is mg
and they gives Lithium nitride and magnesium nitride
Mg and Li are similar in their properties due to
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Same e/m ratio
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same electron afinity
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same group
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same ionic potential
Explanation
$$ Li $$ and $$ Mg $$ ions have similar polarising power or ionic potential.
Hence, Option "D" is the correct answer.
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