s-Block Elements Important MCQs*

Ruhul Amin Alig

MCQs*

Question: From NCERT NEET2021

Among the following alkaline earth metal halides,

one which is covalent and soluble in organic solvents is:

1. Magnesium chloride

2. Beryllium chloride

3. Calcium chloride

4. Strontium chloride

Subtopic: Chemical Properties |

Answer ▽

Because of small size , $B e^{2 +}$ has the highest polarising power and

hence $B e C l_{2}$ has the highest covalent character and is thus soluble in organic solvents .

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Question: From NCERT NEET 2021

The structures of beryllium chloride in solid state and vapour phase, are :

1. Dimer and Linear, respectively.

2. Chain in both.

3. Chain and dimer, respectively.

4. Linear in both.

Subtopic: Reasoning Questions |

Answer ▽

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Question: From NCERT NEET2020

HCl was passed through a solution of CaCl2, MgCl2 and NaCl. Compound(s) that gets crystallise is -

1. Only NaCl

2. Only MgCl2

3. NaCl, MgCl2 and CaCl2

4. Both MgCl2 and CaCl2

Subtopic: Reasoning Questions |Equillibrium Common ion effect

Answer ▽

When $H C l$ is passed through the mixture $C l^{-}$ ion concentration increases.

Hence ionic product $[N a^{+}] [C l^{-}]$ becomes more than solubility product.

So, NaCl will precipitate out.

Filtrate $⟶ H C l g a s p a s s e d$ pure NaCl precipitation (common ion effect)

Calcium and magnesium chloride being more soluble than NaCl remain in the solution.

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Question: From NCERT Derived PYQ

The solubility of $C a F_{2} (K_{s p} = 3.4 \times 1 0^{- 11})$ in 0.1M solution of NaF would be:

$3.4 \times 1 0^{- 12} M$

$3.4 \times 1 0^{- 10} M$

$3.4 \times 1 0^{- 9} M$

$3.4 \times 1 0^{- 13} M$

Medium

Answer ▽

Correct option is

$3.4 \times 1 0^{- 9} M$

The dissociation equilibrium of calcium fluoride is as given below.
$C a F_{2} ⇌ x C a^{2 +} + 2 x 2 F^{-}$

The dissociation of NaF is as shown below.
$N a F \to 0.1 N a^{+} + 0.1 F^{-}$

Thus total fluoride ion concentration is $2 x + 0.1$ M but $2 x < < < 0.1$ .

Hence, 2x is neglected and the total fluoride ion concentration is 0.1 M.

The expression for the solubility product is as follows.
$K_{s p} = [C a^{2 +}] [F^{-}]^{2}$

Substitute values in the above expression:
$3.4 \times 1 0^{- 11} = x (0.1)^{2}$ or $x = 3.4 \times 1 0^{- 9}$ M.

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Question: From NCERTDerived PYQ

One litre of water contains $10^{- 7}$ mole of $H^{+}$ ions. Degree of ionisation of water is:

$1.8 \times 10^{- 7}$

$0.8 \times 10^{- 9}$

$5.4 \times 10^{- 9}$

$5.4 \times 10^{- 7}$

Easy

Chapter-Equilibrium

Answer ▽

Correct option is

$1.8 \times 10^{- 7}$

$H_{2} O ⇌ H^{+} + O H^{-}$
$C$ $0$ $0$
$C (1 - α)$ $C α$ $C α$

$C α = 1 0^{- 7}$

[H2O] = $\frac{1 0 0 0}{1 8}$ = 55.55 M

C= 55.5M

So $α = 18 \times 1 0^{- 10}$

In percentage $α = 1.8 \times 1 0^{- 7}$ %

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Question: From NCERT Derived PYQ

Which one of the following compounds liberates $C O_{2}$ from aqueous $N a H C O_{3}$ ?

Anilinium chloride ( $C_{6} H_{8} C l N$ )

$C H C l_{3}$

$C C l_{4}$

$C H_{3} C l$

Medium

Answer ▽

Correct option is

Anilinium chloride ( $C_{6} H_{8} C l N$ )

Anilinium chloride is the hydrochloride salt of aniline. It reacts with aqueous sodium bicarbonate to liberate carbon dioxide. Chloroform, carbon tetrachloride and methyl chloride are solvents. They do not react with sodium bicarbonate.

$C_{6} H_{5} N H_{3}^{+} C l^{-} + N a H C O_{3} C_{6} H_{5} N H_{2} + N a C l + H_{2} O + C O_{2}$

Hence, the correct option is $A$

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Question: From NCERT NEET 2020

Identify the correct statement from the following.

1. The order of hydration enthalpies of alkaline earth cations
Be2+ < Mg2+ < Ca2+ < Sr2+ < Ba2+

2. Lithium and Magnesium show some similarities in their physical properties as they are diagonally placed in the periodic tables.

3. Lithium is softer among all alkali metals.

4. Lithium chloride is deliquescent and crystallizes as a hydrate, LiCl·6H2O.

Answer ▽

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Question: From NCERT NEET 2020

What is the role of gypsum, CaSO4.2H2O in setting of cement? Identify the correct option from the following:

(1) To fasten the setting process

(2) To provide water molecules for hydration process

(3) To help to remove water molecules

(4) To slow down the setting process

Subtopic: Preparations,Properties & Uses of S Block Elements |

Answer ▽

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Question: From NCERT NEET 2019

Which of the following is an amphoteric hydroxide?

1. $Be {(OH)}_{2}$

2. $Sr {(OH)}_{2}$

3. $Ca {(OH)}_{2}$

4. $Mg {(OH)}_{2}$

Answer ▽

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Question: From NCERT NEET 2019

Crude sodium chloride obtained by crystallization of brine solution does not contain-

(1) $M g S O_{4}$

(2) $N a_{2} S O_{4}$

(3) $M g C l_{2}$

(4) $C a S O_{4}$

Subtopic: Compounds of Ca and Na -Preparations,Properties & Uses |

Answer ▽

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Question: From NCERT NEET 2019

Which of the alkali metal choride (MCl) forms its dehydrate salt (MCl. $2 H_{2} O$ ) easily?

(1) LiCl

(2) CsCl

(3) RbCl

(4) KCl

Answer ▽

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Question: From NCERT Derived PYQ

The alkali metal which forms hydrate of chloride salt is:
A.Li
B.Na
C.Rb
D.Cs

Answer ▽

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Question: From NCERT NEET 2018

The most acidic oxide among the following is -

1. MgO

2. BeO

3. BaO

3. CaO

Answer ▽

In metals moving down the group metallic character increases, so basic nature increases hence most acidic will be $B e O$ as Be is least metallic in group 2 elements.

BeO is most acidic in nature as the acidity of oxides decreases with increases in the electropositive character of the central atom

Hint:
All the given oxides belong to the second group of periodic tables. And we also know that moving down the group metallic character increases and Electronegativity decreases down the group. Now try to relate these properties to come up with the correct solution.

Complete step by step answer:
Electronegativity: It measures the pull of an atom of a component on the electrons during a bond (covalent). The stronger its pulling power the upper its electronegativity. Electronegativity increases from left to right across a period. because the nuclear charge increases from one element to subsequent across the amount the additional electrons enter to an equivalent shell. Thus there is, in effect, a greater pull on electrons which are an equivalent distance away. Electronegativity decreases down a group. As a group is descended the outer shell of electrons gets beyond the positive nucleus therefore the pull on these electrons gets less from one element to subsequent. The foremost electronegative element is fluorine(F), followed by oxygen(O).

The Group 2 alkaline-earth metal metals include Beryllium, Magnesium, Calcium, Barium, Strontium and Radium and are soft, silver metals that are less metallic in character than the Group 1 Alkali Metals. Although many characteristics are common throughout the group, the heavier metals like Ca, Sr, Ba, and Ra are almost as reactive because the Group 1 Alkali Metals. All the weather in Group 2 has two electrons in their valence shells, giving them an oxidation number of +2.
In metals moving down the group metallic character increases, so basic nature increases hence most acidic are going to be BeO as Be is least metallic in group 2 elements.
BeO is most acidic in nature because the acidity of oxides decreases with increases within the electropositive character of the central atom.
Thus, the correct option is A.

Note:
As for any group within the table the Group 2 atoms get larger. So do their ions. The ions have a charge of +2 when the atoms lose the 2 outermost-level electrons, leaving this level empty. The 2 electrons of the

B e^{2 +}

ion occupy the primary energy state only therefore the ion is extremely small. Ions like this, small and highly charged, have a high charge density and therefore the charge density of the

B e^{2 +}

ion is extremely high indeed. Due to this the properties of beryllium and its compounds aren't typical of the opposite Group 2 elements.

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Question: From NCERT NEET 2017

Ionic mobility of which of the following alkali metal ions is lowest when an aqueous solution of their salts are put under an electric field?

(1) Na

(2) K

(3) Rb

(4) Li

Answer ▽

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Question: From NCERT NEET 2016

The suspension of slaked lime in water is known as -

1. Limewater.

2. Quicklime.

3. Milk of lime.

4. Aqueous solution of slaked lime.

Answer ▽

3 The suspension of slaked lime in water is known as milk of lime i.e $C a (O H)_{2}$ .
Slaked lime is CaO.
Reaction is $C a O + H_{2} O \to C a (O H)_{2}$ .
Hence, option A is correct answer.

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Question: From NCERT Derived PYQ

Which of the following alkali metal carbonates is the least stable and decomposes more readily?

$L i_{2} C O_{3}$

$N a_{2} C O_{3}$

$K_{2} C O_{3}$

$C s_{2} C O_{3}$

Medium

Answer ▽

Correct option is

$L i_{2} C O_{3}$

On lithium carbonate decomposes to form lithium monoxide and carbon dioxide. Other alkali metal carbonates do not decompose easily on heating.

$L i_{2} C O_{3} \to L i_{2} O + C O_{2}$

Hence, the correct option is $A$

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Question: From NCERT NEET 2016

The incorrect statement among the following regarding Beryllium is-

(1) It is rendered passive by nitric acid.

(2) lt forms Be2C

(3) It's salts rarely hydrolyse.

(4) It's hydride is electron-deficient and polymeric.

Answer ▽

$(A) Be-Salts are highly covalent and hence are easily hydrolysed. (B) (B e H_{2})_{n} [Beryllium hydride] is electron deficient and is in polymeric form. (c) Beryllium is not soluble in dilute or cold nitric acid, but is readily dissolved by hot concentrated nitric acid. (D) Beryllium forms carbide, B e_{2} C .$

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Question: From NCERT NEET Derived PYQ

Which one of the following represents a correct sequence of reducing the power of the following elements (in aq solution)?

$L i > C s > R b$

$R b > C s > L i$

$C s > L i > R b$

$L i > R b > C s$

Medium

Answer ▽

Correct option is

$L i > C s > R b$

Due to their low ionization energies, all alkali metals are good reducing agents. Their reducing character changes from: $L i > C s > R b > K > N a$
The reducing character is measured in the terms of electrode potential.
Element
$E^{o}$ (V) at 298K
$L$
$-$
$a$
$-$
$K$
$-$
$b$
$-$
$s$
$-$

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Question: From NCERT Derived PYQ

Among the elements belonging to the 4th period____has the maximum reducing power.

Ge

Ca

Br

K

Medium

Answer ▽

Correct option is

K

The reducing power of elements decreases along the period towards the right. Thus the group IA elements have maximum reducing power. Hence K has the maximum reducing power.

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Question: From NCERT Derived PYQ

The element exhibiting most stable $+ 2$ oxidation state among the following is

$A g$

$F e$

$S n$

$P b$

Answer ▽

Correct option is

$P b$

$A g$ has the electronic configuration $[K r] 4 d^{10} 5 s^{1}$ Hence $+ 1$ is a stable oxidation state for it.

$F e^{3 +}$ ion is more stable due to its half-filled $3 d^{5}$ electron configuration. As half filled and completely filled shells are more stable $F e^{3 +}$ ion is more stable than $F e^{2 +}$

The $S n^{2 +}$ ions convert to $S n^{4 +}$ ions because the tin(IV) oxidation state is more stable than tin(II).

In non-transition elements of p-block, lower oxidation state is $m$ stable due to inert pair effect e.g., $P b^{2 +}$ is more stable than $P b^{4 +}$

Hence option $(D)$ is correct.

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Question: From NCERT Derived PYQ

The radius of hydrogen atom in the ground state is 0.53 $\overset{˚}{A}$ . The radius of $L i^{2 +}$ ion (atomic number = 3) in a similar state is

$0.17 \overset{˚}{A}$

$0.265 \overset{˚}{A}$

$3 \overset{˚}{A}$

$0.53 \overset{˚}{A}$

Medium

Answer ▽

Correct option is

$0.17 \overset{˚}{A}$

$By Bohr’s Theory :$

$Atomic Radius of an atom = 0.53 \times \frac{n ^{2}}{z} A where n = Principle quantum number z = Atomic number$

$Given L i^{+ 2} ion$

$γ = 0.53 \times \frac{1}{3}, n = 1 for ground state = 0.176 A$

$Radius of L i^{† 2} ion in ground state = 0.176 \hat{A}$

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Question: From NCERT NEET 2016

The product obtained as a result of a reaction of nitrogen with CaC2 is .

1. CaCN
2. CaCN3
3. Ca2CN
4. CaCN2

Answer ▽

Correct option is

$C a (C N)_{2}$

The product obtained as a result of a reaction of nitrogen with calcium carbide ( $C a C_{2}$ ) is calcium cyanide

The reaction takes place at temperature around $300$ to $350$ $^{o} C$ .

$C a C_{2} + N_{2} 300 - 35 0^{o} C C a (C N)_{2}$ .

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Question: From NCERT Derived PYQ

$C a + C_{2} \to C a C_{2} N_{2} A$
Compound ( A ) is used as a / an :

fertilizer

dehydrating agent

oxidising agent

reducing agent

Easy

Answer ▽

Correct option is

fertilizer

Calcium carbide reacts with nitrogen at high temperature to form calcium cyanamide which is used as fertilizer.
$C a + C_{2} \to C a C_{2} N_{2} C a C N_{2} + C$

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Question: From NCERT Derived PYQ

The number of carbon compounds is very large because it:

is tetravalent

forms double and triple bond

is non metal

shows catenation

Easy

Answer ▽

Correct option is

shows catenation

The number of carbon compounds is very large because it shows catenation.
Catenation is the linkage of atoms of the same element into longer chains.
Carbon forms covalent bonds with other carbon atoms to form longer chains and structures.

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Question: From NCERT NEET 2016

Which of the following statements is false?

1. Ca2+ ions are important in blood clotting
2. Ca2+ ions are not important in maintaining the regular beating of the heart
3. Mg2+ ions are important in the green parts of plants
4. Mg2+ ions form a complex with ATP

Subtopic: Biological Importance of S Block Elements and & Its Ore |

Answer ▽

$C a^{2 +}$ ions are important in maintaining the regular beating of the heart. $C a^{2 +}$ ions are also important in blood clotting and are required to trigger the contraction of muscle.

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Question: From NCERT NEET 2015

"Metals are usually not found as nitrates in their ores'"

Out of the following two (I and II) reasons which is/are true for the above observation?

I. Metal nitrates are highly unstable.

II. Metal nitrates are highly soluble in water.

1. I and ll are true

2. I and II are false

3. I is false but ll is true

4. l is true but ll is tase

Answer ▽

Metal nitrates such as potassium nitrate, sodium nitrate are stable. The statement ( $b$ ) "Metal nitrates are highly soluble in water" is true.

Metal nitrates such as potassium nitrate, sodium nitrate have high water solubility. Hence, they are washed out by rainwater and not found in the ores.

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Question: From NCERT NEET 2015

Solubility of the alkaline earth's metal sulphates in water decreases in the sequence-

1. Mg > Ca > Sr > Ba

2. Ca > Sr > Ba > Mg

3. Sr > Ca > Mg > Ba

4. Ba > Mg > Sr > Ca

Answer ▽

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Question: From NCERT NEET 2015

A compound that releases CO2 most easily upon heating is -

1. K2CO3

2. Na2CO3

3. MgCO3

4. CaCO3

Answer ▽

On heating, $M g C O_{3},$ $C O_{2}$ releases most easily. This is due to the small size of the resulting oxide ion.
The radii of the oxide ion and $M g^{2 +}$ ion are nearly same and hence they pack together tightly with the result its formation (i.e decomposition of its carbonate) is easy and requires less energy.

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Question: From NCERT NEET 2015

A compound that releases CO2 most easily upon heating is -

1. $K_{2} C O_{3}$

2. $N a_{2} C O_{3}$

3. $M g C O_{3}$

4. $C a C O_{3}$

Answer ▽

On heating, $M g C O_{3},$ $C O_{2}$ releases most easily. This is due to the small size of the resulting oxide ion.
The radii of the oxide ion and $M g^{2 +}$ ion are nearly same and hence they pack together tightly with the result its formation (i.e decomposition of its carbonate) is easy and requires less energy.

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Question: From NCERT Derived PYQ

Which is decomposed most easily?

$C a C O_{3}$

$M g C O_{3}$

$B a C O_{3}$

Equally

Medium

Answer ▽

Correct option is

$M g C O_{3}$

$M C O_{3} \to M O + - 394.4 C O_{2}$
$M g - 1028.2 - 568.964.9 C a - 1129.2603.4165.9 B a - 1134.4 - 520.4219.6$
As second value is negative for both Ba and Ca so they are more stable
and $M g C O_{3}$ is least stable so it will decompose easily.

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Question: From NCERT NEET 2011

An active ingredient in bleaching powder for bleaching action is -

1. Ca(OCl)2

2. CaO2Cl

3. CaCl2

4. CaOCl2

Answer ▽

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Question: From NCERT NEET2010

An alkaline earth metal sulphates that has hydration enthalpy higher than the lattice enthalpy is -

1. CaSO4

2. BeSO4

3. BaSO4

4. SrSO4

Answer ▽

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Question: From NCERT NEET 2010

Property of the alkaline earth metals that increases with their atomic number is -

1. Solubility of their hydroxides in water.

2. Solubility of their sulphates in water.

3. Ionisation energy.

4. Electronegativity.

Answer ▽

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Question: From NCERT NEET 2009

In the case of alkali metals, the covalent character decreases in the order

1. MCl>MI>MBr>MF

2. MF>MCl>MBr>MI

3. MF>MCl>MI>MBr

4. MI>MBr>MCl>MF

Answer ▽

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Question: From NCERT NEET 2008

The thermal stability of these hydrides decreases in which of the following orders?

(1) CsH > RbH > KH > NaH > LiH

(2) KH > NaH > LiH > CsH > RbH

(3) NaH > LiH > KH > RbH > CsH

(4) LiH > NaH > KH > RbH > CsH

Answer ▽

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Question: From NCERT Derived PYQ

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s-Block Elements Important MCQs*

The solubility of CaF2​(Ksp​=3.4×10−11) in 0.1M solution of NaF would be:

3.4×10−12M

3.4×10−10M

3.4×10−9M

3.4×10−13M

3.4×10−9M

One litre of water contains 10−7 mole of H+ ions. Degree of ionisation of water is:

1.8×10−7

0.8×10−9

5.4×10−9

5.4×10−7

1.8×10−7

H2​O⇌H++OH− C 0 0C(1−α) Cα CαCα=10−7[H2O] =181000​= 55.55 M C= 55.5MSo α=18×10−10In percentage α=1.8×10−7%

Which one of the following compounds liberates CO2​ from aqueous NaHCO3​?

Anilinium chloride (C6​H8​ClN)

CHCl3​

CCl4​

CH3​Cl

Anilinium chloride (C6​H8​ClN)

The alkali metal which forms hydrate of chloride salt is:A.LiB.NaC.RbD.Cs

In metals moving down the group metallic character increases, so basic nature increases hence most acidic will be BeO as Be is least metallic in group 2 elements.BeO is most acidic in nature as the acidity of oxides decreases with increases in the electropositive character of the central atom

3

The suspension of slaked lime in water is known as milk of lime i.e Ca(OH)2​.Slaked lime is CaO.Reaction is CaO+H2​O→Ca(OH)2​.Hence, option A is correct answer.

Which of the following alkali metal carbonates is the least stable and decomposes more readily?

Li2​CO3​

Na2​CO3​

K2​CO3​

Cs2​CO3​

Li2​CO3​

On lithium carbonate decomposes to form lithium monoxide and carbon dioxide. Other alkali metal carbonates do not decompose easily on heating.Li2​CO3​→Li2​O+CO2​Hence, the correct option is A

Which one of the following represents a correct sequence of reducing the power of the following elements (in aq solution)?

Li>Cs>Rb

Rb>Cs>Li

Cs>Li>Rb

Li>Rb>Cs

Li>Cs>Rb

Due to their low ionization energies, all alkali metals are good reducing agents. Their reducing character changes from: Li>Cs>Rb>K>NaThe reducing character is measured in the terms of electrode potential.ElementEo(V) at 298KL−a−K−b−s−

Among the elements belonging to the 4th period____has the maximum reducing power.

Ge

Ca

Br

K

K

The reducing power of elements decreases along the period towards the right. Thus the group IA elements have maximum reducing power. Hence K has the maximum reducing power.

The element exhibiting most stable +2 oxidation state among the following is

Ag

Fe

Sn

Pb

Pb

The radius of hydrogen atom in the ground state is 0.53 A˚. The radius of Li2+ ion (atomic number = 3) in a similar state is

0.17A˚

0.265A˚

3A˚

0.53A˚

0.17A˚

By Bohr’s Theory : Atomic Radius of an atom =0.53×zn2​ A where n= Principle quantum number z= Atomic number ​ Given Li+2 ion γ​=0.53×31​,n=1 for ground state =0.176 A​ Radius of Li†2 ion in ground state =0.176A^

Ca(CN)2​

The product obtained as a result of a reaction of nitrogen with calcium carbide (CaC2​) is calcium cyanideThe reaction takes place at temperature around 300 to 350 oC. CaC2​+N2​300−350oC​Ca(CN)2​.

Ca+C2​→CaC2​N2​​ACompound ( A ) is used as a / an :

fertilizer

dehydrating agent

oxidising agent

reducing agent

fertilizer

Calcium carbide reacts with nitrogen at high temperature to form calcium cyanamide which is used as fertilizer.Ca+C2​→CaC2​N2​​CaCN2​+C

The number of carbon compounds is very large because it:

is tetravalent

forms double and triple bond

is non metal

shows catenation

shows catenation

The number of carbon compounds is very large because it shows catenation.Catenation is the linkage of atoms of the same element into longer chains.Carbon forms covalent bonds with other carbon atoms to form longer chains and structures.

Ca2+ ions are important in maintaining the regular beating of the heart. Ca2+ ions are also important in blood clotting and are required to trigger the contraction of muscle.

Metal nitrates such as potassium nitrate, sodium nitrate are stable. The statement (b) "Metal nitrates are highly soluble in water" is true. Metal nitrates such as potassium nitrate, sodium nitrate have high water solubility. Hence, they are washed out by rainwater and not found in the ores.

Which is decomposed most easily?

CaCO3​

MgCO3​

The solubility of $C a F_{2} (K_{s p} = 3.4 \times 1 0^{- 11})$ in 0.1M solution of NaF would be:

$3.4 \times 1 0^{- 12} M$

$3.4 \times 1 0^{- 10} M$

$3.4 \times 1 0^{- 9} M$

$3.4 \times 1 0^{- 13} M$

$3.4 \times 1 0^{- 9} M$

One litre of water contains $10^{- 7}$ mole of $H^{+}$ ions. Degree of ionisation of water is:

$1.8 \times 10^{- 7}$

$0.8 \times 10^{- 9}$

$5.4 \times 10^{- 9}$

$5.4 \times 10^{- 7}$

$1.8 \times 10^{- 7}$

$H_{2} O ⇌ H^{+} + O H^{-}$
$C$ $0$ $0$
$C (1 - α)$ $C α$ $C α$

$C α = 1 0^{- 7}$

[H2O] = $\frac{1 0 0 0}{1 8}$ = 55.55 M

C= 55.5M

So $α = 18 \times 1 0^{- 10}$

In percentage $α = 1.8 \times 1 0^{- 7}$ %

Which one of the following compounds liberates $C O_{2}$ from aqueous $N a H C O_{3}$ ?

Anilinium chloride ( $C_{6} H_{8} C l N$ )

$C H C l_{3}$

$C C l_{4}$

$C H_{3} C l$

Anilinium chloride ( $C_{6} H_{8} C l N$ )

The alkali metal which forms hydrate of chloride salt is:
A.Li
B.Na
C.Rb
D.Cs

In metals moving down the group metallic character increases, so basic nature increases hence most acidic will be $B e O$ as Be is least metallic in group 2 elements.

BeO is most acidic in nature as the acidity of oxides decreases with increases in the electropositive character of the central atom

The suspension of slaked lime in water is known as milk of lime i.e $C a (O H)_{2}$ .
Slaked lime is CaO.
Reaction is $C a O + H_{2} O \to C a (O H)_{2}$ .
Hence, option A is correct answer.

$L i_{2} C O_{3}$

$N a_{2} C O_{3}$

$K_{2} C O_{3}$

$C s_{2} C O_{3}$

$L i_{2} C O_{3}$

On lithium carbonate decomposes to form lithium monoxide and carbon dioxide. Other alkali metal carbonates do not decompose easily on heating.

$L i_{2} C O_{3} \to L i_{2} O + C O_{2}$

Hence, the correct option is $A$

$L i > C s > R b$

$R b > C s > L i$

$C s > L i > R b$

$L i > R b > C s$

$L i > C s > R b$

Due to their low ionization energies, all alkali metals are good reducing agents. Their reducing character changes from: $L i > C s > R b > K > N a$
The reducing character is measured in the terms of electrode potential.
Element
$E^{o}$ (V) at 298K
$L$
$-$
$a$
$-$
$K$
$-$
$b$
$-$
$s$
$-$

The element exhibiting most stable $+ 2$ oxidation state among the following is

$A g$

$F e$

$S n$

$P b$

$P b$

The radius of hydrogen atom in the ground state is 0.53 $\overset{˚}{A}$ . The radius of $L i^{2 +}$ ion (atomic number = 3) in a similar state is

$0.17 \overset{˚}{A}$

$0.265 \overset{˚}{A}$

$3 \overset{˚}{A}$

$0.53 \overset{˚}{A}$

$0.17 \overset{˚}{A}$

$By Bohr’s Theory :$

$Atomic Radius of an atom = 0.53 \times \frac{n ^{2}}{z} A where n = Principle quantum number z = Atomic number$

$Given L i^{+ 2} ion$

$γ = 0.53 \times \frac{1}{3}, n = 1 for ground state = 0.176 A$

$Radius of L i^{† 2} ion in ground state = 0.176 \hat{A}$

$C a (C N)_{2}$

The product obtained as a result of a reaction of nitrogen with calcium carbide ( $C a C_{2}$ ) is calcium cyanide

The reaction takes place at temperature around $300$ to $350$ $^{o} C$ .

$C a C_{2} + N_{2} 300 - 35 0^{o} C C a (C N)_{2}$ .

$C a + C_{2} \to C a C_{2} N_{2} A$
Compound ( A ) is used as a / an :

Calcium carbide reacts with nitrogen at high temperature to form calcium cyanamide which is used as fertilizer.
$C a + C_{2} \to C a C_{2} N_{2} C a C N_{2} + C$

The number of carbon compounds is very large because it shows catenation.
Catenation is the linkage of atoms of the same element into longer chains.
Carbon forms covalent bonds with other carbon atoms to form longer chains and structures.

$C a^{2 +}$ ions are important in maintaining the regular beating of the heart. $C a^{2 +}$ ions are also important in blood clotting and are required to trigger the contraction of muscle.

Metal nitrates such as potassium nitrate, sodium nitrate are stable. The statement ( $b$ ) "Metal nitrates are highly soluble in water" is true.

Metal nitrates such as potassium nitrate, sodium nitrate have high water solubility. Hence, they are washed out by rainwater and not found in the ores.

$C a C O_{3}$

$M g C O_{3}$

$B a C O_{3}$

$M g C O_{3}$

$M C O_{3} \to M O + - 394.4 C O_{2}$
$M g - 1028.2 - 568.964.9 C a - 1129.2603.4165.9 B a - 1134.4 - 520.4219.6$
As second value is negative for both Ba and Ca so they are more stable
and $M g C O_{3}$ is least stable so it will decompose easily.