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

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

Cement, the important building material is a mixture of oxides of several elements. Besides calcium, iron and sulphur, oxides of elements of which of the group (s) are present in the mixture?

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. Group 2

  2. Groups 2, 13 and 14

  3. Groups 2 and 13

  4. Groups 2 and 14

Show answer
Correct Option: B
Explanation:
Cement is a mixture of calcium (present in group 2) and aluminium silicates (contains group 13 and 14 elements).

Cement is a mixture of:

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. calcium silicates

  2. calcium aluminates

  3. calcium silicates and aluminates

  4. none of these

Show answer
Correct Option: C
Explanation:

Cement is an important building material. It is also called Portland cement. Important ingredients of Portland cement are dicalcium silicate $\left( { Ca } _{ 2 }{ SiO } _{ 4 } \right) 26$%, tricalcium silicate $\left( { Ca } _{ 3 }{ SiO } _{ 5 } \right) 51$% and tricalcium aluminate$\left( { Ca } _{ 3 }{ Al } _{ 2 }{ O } _{ 6 } \right) 11$%.


Hence, cement is a mixture of calcium silicates and aluminates.

For the manufacture of cement various steps are given below. Arrange the steps in a proper sequence.


(a) Clinker formation                            (b) Crushing
(c) Addition of gypsum                         (d) Mixing of raw materials
(e) Grinding to fine powder                  (f) Calcination in rotary kiln

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. d b f a c e

  2. b d f c e a

  3. d c a f e b

  4. a b c d e f

Show answer
Correct Option: A
Explanation:
The order of steps followed in the formation of cement is :
(i) Mixing of raw materials $(d)$
(ii) Crushing $(b)$
(iii) Calcination in a rotary kiln $(f)$
(iv) Clinker formation $(a)$
(v) Addition Gypsum $(c)$
(vi) Grinding to line powder $(e)$


Hence, the correct option is $(A)$.

$ Y\xleftarrow[]{\Delta,205^{\circ}C} CaSO 4.2H _2O\  \xrightarrow[]{\Delta,120^{\circ}C} X $. 


$X$ and $Y$ are respectively _____.

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. plaster of paris, dead burnt plaster

  2. dead burnt plaster, plaster of paris

  3. $CaO$, plaster of paris

  4. plaster of paris, mixture of gases

Show answer
Correct Option: A
Explanation:

Reaction of process:


  $CaSO _4 \xleftarrow[]{\Delta,205^{\circ}C} CaSO _4.2H _2O \xrightarrow[]{\Delta,120^{\circ}C} CaSO _4.(1/2)H _2O$                                                                                           (dead burnt plaster)                                          (plaster of paris)
Anhydrous Calcium sulphate is known as dead burnt plaster and $CaSO _4.\cfrac{1}{2} H _2O$ is called plaster of paris.
Hence, the correct option is $A$.

In the hardening stage of plaster of paris, the compound formed is :

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. $CaSO _{4}$

  2. orthorhombic $CaSO _{4} . 2H _{2}O$

  3. $CaSO _{4} . H _{2}O$

  4. monoclinic $CaSO _{4} . 2H _{2}O$

Show answer
Correct Option: D
Explanation:

$\underset{\text{plaster of paris}}{CaSO _4.1/2H _2O} \xrightarrow[\text{setting}]{H _2O} \underset{\begin{matrix}\text{gypsum}\\text{orthorhombic}\\text{dihydrate}\end{matrix}}{CaSO _4.2H _2O} \xleftarrow[\text{hardening}]{} \underset{\begin{matrix} \text{gypsum} \\text{monoclinic dihydrate}\end{matrix}}{CaSO _4.2H _2O}$
The plaster of paris absorbs water to form orthorhombic calcium sulfate dihydrate which sets to form a hard mass containing monoclinic $CaSO _4.2H _2O$.

Gypsum is added to clinker during cement manufacturing to:

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. Decrease the rate of setting of cement

  2. Bind the particles of calcium silicate

  3. Facilitate the formation of colloidal gel

  4. All of the above

Show answer
Correct Option: A
Explanation:

During the cement manufacturing process, upon the cooling of the clinker, a small amount of gypsum is introduced during the final grinding process. Gypsum is added to control the setting of cement. 


If not added, the cement will set immediately after mixing water leaving no time for concrete placing. Hence, the addition of gypsum is required to decrease the rate of setting.


Hence, option $(A)$ is correct.

The molecular formula of gypsum is :

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. $CaSO _{4}.H _{2}O$

  2. $CaSO _{4}.2H _{2}O$

  3. $2CaSO _{4}.H _{2}O$

  4. $CaSO _{4}.3H _{2}O$

Show answer
Correct Option: B
Explanation:

Gypsum is calcium sulphate dihydrate. Its molecular formula is $ CaSO _{4} \cdot2H _{2}O $. It is an ore of calcium.