Tag: the s-block elements (alkali and alkaline earth metals)

Questions Related to the s-block elements (alkali and alkaline earth metals)

Choose the correct answer form the alternatives given.
Which of the following has lowest thermal stability?

chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

  1. $Li _2CO _3$

  2. $Na _2CO _3$

  3. $K _2CO _3$

  4. $Rb _2CO _3$

Show answer
Correct Option: A
Explanation:

Lithium carbonates are least thermal stable compound which decompose upon heating to give lithium oxide and carbon dioxide.
$ { Li } _{ 2 }C{ O } _{ 3 }\ \rightarrow {  Li } _{ 2 }O\ +\ C{ O } _{ 2 } $

Fill up the blanks with appropriate choices.
Lithium and magnesium react slowly with water. Their hydroxides are ________ soluble in water. Carbonates are Li and Mg ________ easily on heating. Both LiCl and $MgCl 2$ are _______ in entanol and are _____. They crystallise from their aqueous solutions as ______.

chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

  1. more, do not decompose, soluble, hygroscopic, hydrates

  2. less, decompose, soluble, deliquescent, hydrates

  3. freely, sublime, insoluble, deliquescent, anhydrous

  4. freely, decompose, soluble, hygroscopic, crystals

Show answer
Correct Option: B
Explanation:

A Diagonal Relationship is said to exist between certain pairs of diagonally adjacent elements in the second and third periods of the periodic table. These pairs (Li & Mg, Be & Al, B & Si etc.) exhibit similar properties.

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

chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

  1. Lithium hydride

  2. Sodium borohydride

  3. Calcium metal

  4. Sodium formate

Show answer
Correct Option: A
Explanation:

  • 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.

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:

chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

  1. ionic nature of lithium fluoride

  2. high lattice enthalpy

  3. high hydration enthalpy for lithium ion

  4. low ionisation enthalpy of lithium atom

Show answer
Correct Option: B
Explanation:

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.

$Li$ has an abnormal behaviour in its group, which is ____________.

chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

  1. lithium carbonate decomposes into its oxide on heating unlike other elements.

  2. $LiCl$ is covalent in nature.

  3. $Li _3N$ is a stable compound.

  4. $LiCl$ is a good conductor of electricity in the molten state.

Show answer
Correct Option: A,B,C
Explanation:

(A). Lithium carbonate, being less stable, decomposes into its oxide on heating, whereas other group IA carbonates are stable and do not decompose.


${ Li } _{ 2 }C{ O } _{ 3 }\ \underrightarrow { \triangle  } \ { Li } _{ 2 }O+C{ O } _{ 2 }$

(B). Lithium halides, except fluoride, are covalent due to fajan's rule.

(C) Lithium is the only 1A metal that can combine with inert nitrogen in air to form lithium nitride.

(D) Lithium chloride , like other alkali metals compounds , is a good conductor of electricity in molten state. 

Alkali metals readily react with oxyacids forming corresponding salts like ${ M } _{ 2 }{ CO } _{ 3 }$, ${ M }H{ CO } _{ 3 }$, ${ M }N{ O } _{ 3 }$, ${ M } _{ 2 }{ SO } _{ 4 }$, etc. with evolution of hydrogen. They also dissolve in liquid ${ NH } _{ 3 }$ but without the evolution of hydrogen. The color of its dilute solution is blue but when it is heated and concentrated then its color becomes bronze.

Which of the following statement about the sulphate of alkali metal is correct :

chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

  1. except ${ Li } _{ 2 }{ SO } _{ 4 }$ all sulphate of other alkali metals are soluble in water.

  2. all sulphates of alkali metals except lithium sulphate forms alum.

  3. the sulphates of alkali metals cannot be hydrolysed.

  4. all of these.

Show answer
Correct Option: D
Explanation:
Except ${ Li } _{ 2 }{ SO } _{ 4 }$ all sulphate of other alkali metals are soluble in water and forms alum. Thus, they form double salts with the sulphates of trivalent metals like $Al, Fe, Cr$ etc. The sulphates of alkali metals cannot be hydrolysed as they are salts of a strong acid and strong base. 

Which of the following statement(s) is/are true?

chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

  1. Both $LiCl$ and $MgCl _{2}$ are deliquescent.

  2. Lithium is least reactive but the strongest reducing agent amongst all the alkali metals.

  3. Liquid sodium metal is used as a coolant in fast breeder nuclear reactors.

  4. Lithium iodide is the most ionic in nature among all alkali metal halides.

Show answer
Correct Option: A,B,C
Explanation:

(A) $Li^{+}$ and $Mg^{2+}$ have higher polarising power and thus attract more number of water molecules.
(B) $Li$ is least reactive because of its highest ionisation energy on account of smaller size.
(C) It is one of the uses of liquid sodium as it has low melting point.
(D) $LiI$ is the most covalent due to smaller cation and bigger anion (according to Fajan's rule).

$LiOH$ reacts with $CO {2}$ to form $Li _{2}CO _{3}$ (atomic mass of $Li = 7)$. The amount of $CO _{2}$ (in g) consumed by $1\ g$ of $LiOH$ is closest to ______.

chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

  1. $0.916$

  2. $1.832$

  3. $0.544$

  4. $1.088$

Show answer
Correct Option: A
Explanation:

Balanced chemical equation is:

$2LiOH+C{ O } _{ 2 }\rightarrow { Li } _{ 2 }C{ O } _{ 3 }+{ H } _{ 2 }O$
Molecular weight of each specie is:
$LiOH$=24 g/mol; $C{ O } _{ 2 }$=44 g/mol; ${ Li } _{ 2 }C{ O } _{ 3 }$= 74 g/mol; ${ H } _{ 2 }O$=18 g/mol
From the reaction:
2 mol of $LiOH$ ($24\times2=48\ g$) consumes 1 mol of $CO _2$ (44 g)
Therefore, 1 g of $LiOH$ will consume $\frac { 1 }{ 48 } \times 44\quad g\quad C{ O } _{ 2 }=0.916\ g\ CO _2$
Option A is the correct answer.

Diagonal relationship of elements in due to same:

chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

  1. size

  2. mass number

  3. atomic number

  4. electron affinity

Show answer
Correct Option: A
Explanation:
In addition to horizontal and vertical trends, there is a diagonal relationship between elements such as Li and Mg, Be and Al, B, and Si, that have an adjacent upper left/lower right relative location in the periodic table. 
These pairs of elements have similar size and electronegativity, resulting in similar properties. 

Diagonal relationships occur because of the directions in the trends of various properties as you move across or down the periodic table. Many of the chemical properties of an element are related to the size of the atom. Hence it is because of the same size.

The reaction of water with slaked lime is studied by ________ .

chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

  1. putting slaked lime into water taken in a test tube

  2. putting a lot of water into slaked lime.

  3. sprinkling a little water on slaked lime.

  4. none of the above method.

Show answer
Correct Option: A