Tag: chemistry

Questions Related to chemistry

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

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. $LiCl$

  2. $LiH$

  3. $Li$

  4. $LiOH$

Show answer
Correct Option: B
Explanation:

The reaction is ,


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


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

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 :

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. $Li _{2}CO _{3}$

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

  3. both (a) and (b)

  4. none of these

Show answer
Correct Option: C
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.

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

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

  2. Na

  3. both (a) and (b)

  4. None of these

Show answer
Correct Option: A
Explanation:

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

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 

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. $L{i _2}Se$

  2. $LiSe$

  3. $LiS{e _2}$

  4. $L{i _3}Se$

Show answer
Correct Option: A
Explanation:

Answer(A):- $Li _2Se$

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

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

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. $Li _2$

  2. ${ Be } _{ 2 }^{ + }$

  3. $Be _2$

  4. $B _2$

Show answer
Correct Option: A

Which of the following carbonate is not stable to heat.

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

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

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. $Li$

  2. $Na$

  3. $Rb$

  4. $K$

Show answer
Correct Option: A

Li has chemical properties most similar 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. Al

  2. Ca

  3. Mg

  4. Ti

Show answer
Correct Option: C
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.

Li resembles to element X which is not the member of alkali metals. The group of X 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. II

  2. III

  3. IV

  4. I

Show answer
Correct Option: A
Explanation:

Li resembles to element X which is not a member of alkali metals. The group of X must be II group, because certain elements of 2nd period show similarity with their diagonal elements in the 3rd period as shown below : Thus, Li resembles Mg, Be resembles Al and B resembles Si. This is called diagonal relationship and is due to the reason that these pairs of element have almost identical ionic radii and polarizing power (i.e. charge/size ratio). Element of second period are known as bridge elements.

So Li is I st group element and the diagonal element Mg is II nd group element.
Hence option A is correct.

$Mg$ and $Li$ and similar in their properties 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. same $\dfrac {e}{m}$ ratio

  2. same electron affinity

  3. same group

  4. same radius

Show answer
Correct Option: D
Explanation:

$Li$ and $Mg$ show diagonal relationship due to the similarity in size (radius), electronegativity, ionisation enthalpy and charge/radius ratio.