Tag: chemistry

Questions Related to chemistry

Correct relation for the size of $Li$ and $Mg$ 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. $Mg>>Li$

  2. $Mg>Li$

  3. $Mg=Li$

  4. $Mg<Li$

Show answer
Correct Option: D
Explanation:

Size of Mg is less than that of Li because of the $Z _{eff}$ of Mg. As the protons are added, electrons are attracted with a greater strength towards the core, making the radius of Mg smaller. 

Which of the following will be sparingly soluble in water?

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. $Ca _3(PO _4) _2$

  2. $CaF _2$

  3. $Mg _3(PO _4)2$

  4. $NaF$

Show answer
Correct Option: C
Explanation:

 Fluorides and phosphates of $Li$ and $Mg$ are sparingly soluble in water whereas those of other alkali metals are soluble in water.

Which of the following will produce $CO _2$ on heating?

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. $BaCO _3$

  2. $Na _2CO _3$

  3. $MgCO _3$

  4. $CaCO _3$

Show answer
Correct Option: C,D
Explanation:

Carbonates of $Li$, $Ca$ $Mg$ decompose on heating and liberate $CO _2$.Carbonates of other alkali metals are stable towards heat and decomposed only by fusion. 

${Li} _{2}{SO} _{4}$ is not isomorphous with sodium sulphate, 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. small size of lithium

  2. high coordination number of lithium

  3. high ionization energy of lithium

  4. none of the above

Show answer
Correct Option: A
Explanation:

Isomorphic compounds have same crystal structure at given temperature and conditions. While $LiSO _4$ and $Na _2SO _4$ are not isomorphous due to the exceptionally small size of Lithium (Li).

The first element of the groups 1 and 2 are different from other members of the respective groups. Their behaviour is more similar to the second element of the following groups. What is this relationship known 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. Anomalous relationship

  2. Periodic relationship

  3. Diagonal relationship

  4. Chemical relationship

Show answer
Correct Option: C
Explanation:
The similarities (in many of properties) between first element of a group and second element of the next group is called diagonal relationship.
Thus, Li ( first element of group 1) shows diagonal relationship with Mg (second element of group 2).
Also, Be ( first element of group 2) shows diagonal relationship with Al (second element of group 13).
Also, B ( first element of group 13) shows diagonal relationship with Si (second element of group 14).

Which of the following does not show the anomalous behaviour of Lithium?

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 reacts with nitrogen to form a nitride

  2. Lithium carbonate decomposes on heating

  3. Lithium nitrate gives $NO _2$ on heating

  4. Lithium is the strongest reducing agent

Show answer
Correct Option: D
Explanation:
Anomalous behavior of lithium is due to extremely small size of lithium. Its cation on account of small size and high nuclear charge, lithium exerts the greatest polarizing effect out of all alkali metals on the negative ion. Consequently, lithium ion possesses a remarkable tendency towards solvation and develops a covalent character in its compounds.

But lithium like other metals of the same group is a strong reducing agent. In fact, Lithium is the strongest reducing agent in aqueous solution.

Thus option D is correct.

The properties of $Li$ are similar to those of $Mg$. This is because:

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 have nearly the same size.

  2. both has their charge to size ratio nearly the same.

  3. both have similar electronic configurations.

  4. both are found together in nature.

Show answer
Correct Option: B
Explanation:
  • The properties of lithium are similar to those of $Mg$ because they are having diagonal relationship.
  • The elements having diagonal relationship show similar properties and the reason is because the both of them will have similar electronegativity and polarising power i.e. charge per size ratio of both the elements are nearly the same.

Choose the correct answer form the alternatives given.
Which of the following statements is not true about alkali metals ?

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. All alkali metals from oxo salts such as carbonates, sulphates and nitrates.

  2. The basic character of oxides increases down the group.

  3. Carbonates and sulphates of lithium are stable and their stability decreases down the group.

  4. Solubility of carbonates and sulphates increases down the group.

Show answer
Correct Option: C
Explanation:
Characteristics of Alkali Metals-
  • Found in column 1A of the periodic table.
  • Have one electron in their outermost layer of electrons.
  • Easily ionized.
  • Silvery, soft, and not dense.
  • Low melting points.
  • Incredibly reactive.
  • They form oxo salts such as carbonates, sulphates and nitrates.
  • The basic character of oxides increases down the group.
  • The acidic character of oxides decreases down the group.
  • Solubility of carbonates and sulphates increases down the group.
  • As we move down the alkali metal group, the electropositive character increases. This causes an increase in the stability of alkali carbonates. However, lithium carbonate is not so stable to heat. This is because lithium carbonate is covalent.
  • Hence option C is not correct about alkali 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.