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

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

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

Which of the following illustrate the anomalous properties of Lithium?

  1. Lithium is softer than the other group I metals
  2. Lithium forms nitride, $Li _3N$ unlike other group I metals

  3. The melting and boiling point of Lithium are comparatively high

  4. none of these
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

Similarities of  lithium with magnesium and dissimilarities with that of the other members of the group

Lithium is a very strong element and is equally strong as magnesium.

Li forms $Li _3N$ with nitrogen.

It has high melting and boiling points. The boiling point of lithium is $1330$ degree centigrade that is comparable to that of magnesium which is $1100$ degrees.

Due to small size, the lithium atom has high ionization energy. Hence, it remains inactive to dry air, slowly reactivity with water, liquid bromine and forms a highly stable hydride unlike other alkali metals.

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

$LiAlH 4$ is obtained by reacting an excess of ____  with an ethereal solution of $AlCl _3$:

  1. $LiCl$
  2. $LiH$
  3. $Li$
  4. $LiOH$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reaction is ,


$4LiH + AlCl _3 \rightarrow LiAlH _4 + 3 LiCl$


by reacting $LiH$ in the presence of dry ether with $AlCl _3$ .

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

There is loss in weight when mixture of $Li _{2}CO _{3}$ and $Na _{2}CO _{3}\cdot10H _{2}O$ is heate strongly. This loss is due to :

  1. $Li _{2}CO _{3}$
  2. $Na _{2}CO _{3}\cdot10H _{2}O$

  3. both (a) and (b)

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Loss in weight due to following reactions:
$Li _{2}CO _{3} \rightarrow Li _{2}O+CO _{2} \uparrow$
$Na _{2}CO _{3}\cdot10H _{2}O \rightarrow Na _{2}CO _{3} + 10H _{2}O \uparrow$
As sodium carbonate is thermally stable so it will not dissociates on heating.

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

Nitrate can be converted into metal oxide on heating in case of :

  1. Li

  2. Na

  3. both (a) and (b)

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Reaction on heating:
$2LiNO _{3} \rightarrow Li _{2}O+2NO _{2}+ \frac{1}{2} O _{2}$
$Mg(NO _{3}) _{2} \rightarrow MgO+2NO _{2}+ \frac{1}{2} O _{2}$
$2NaNO _3\rightarrow 2NaNO _2+O _2$

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

Lithium selenide can be described as a cubic closest-packed array of selenide ions with lithium ions in all of the tetrahedral holes. Formula of lithium selenide is 

  1. $L{i _2}Se$
  2. $LiSe$
  3. $LiS{e _2}$
  4. $L{i _3}Se$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer(A):- $Li _2Se$

If number of Se =Z , Number of Li = 2Z

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

Which one of the following species dose not exist under normal conditions?

  1. $Li _2$
  2. ${ Be } _{ 2 }^{ + }$
  3. $Be _2$
  4. $B _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Li2 (dilithium) does not exist under normal conditions due to poor orbital overlap and bond formation. Be2+ exists as the beryllium(II) ion, Be2 as a molecule is unstable but Be2+ is common. B2 exists as a diatomic molecule (paramagnetic with 2 unpaired electrons). The question asks which doesn't exist - Li2 is the correct answer.

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

Which of the following carbonate is not stable to heat.

  1. $Li _2CO _3$
  2. $Na _2CO _3$
  3. $K _2CO _3$
  4. $Rb _2CO _3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Li2CO3 is unstable to heat and decomposes to Li2O + CO2 at lower temperatures. Other alkali metal carbonates (Na2CO3, K2CO3, Rb2CO3) are thermally stable due to larger cation size. This is a unique property of lithium carbonate.

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

Which one of the alkali metals,forms only,the normal oxide $M _2O$ on heating in air?

  1. $Li$
  2. $Na$
  3. $Rb$
  4. $K$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Lithium forms only the normal oxide Li2O on heating in air. Sodium forms Na2O2 (peroxide), and potassium/rubidium form superoxides (KO2, RbO2) under similar conditions. This is due to the small size of Li+ ion.

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

Li has chemical properties most similar to :

  1. Al

  2. Ca

  3. Mg

  4. Ti
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Li has chemical properties most similar to Mg due to diagonal relationship.
Both exhibits same properties like
(i).

$MgCO _3\, \overset{\Delta}{\rightarrow}\, MgO\, +\, CO _2$
$Li _2CO _3\, \overset{\Delta}{\rightarrow}\, Li _2O\, +\, CO _2$

(ii).
$3Mg\, +\, N _2\, \rightarrow Mg _3N _2$ 
$6Li+ N _2 \rightarrow 2Li _3N$

Hence option C is correct answer.