Tag: the s-block elements

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Questions Related to the s-block elements

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

During the manufacturing of single superphosphate, excess silicon combines with acid to form:

  1. silicates

  2. silicic acid

  3. silanes

  4. hydride of silicon
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reactions occurring  during the production of superphosphate are complex and are usually summarised as follows :

1. $Ca _5(PO _4) _3 F + 5H _2SO _4 \rightarrow 5CaSO _4 + 3H _3PO _4 + HF$
2. $Ca _5(PO _4) _3F + 7H _3 PO _4 + 5H _2O \rightarrow 5Ca(H _2PO _4) _2 H _2O + HF$
These reactions can be combined to give the overall equation :
$2Ca _5(PO _4) _3F + 7H _2SO _4 + 3 H _2O \rightarrow 7CaSO _4 + 3Ca(H _2PO _4) _2 H _2O + 2HF$
There are other reactions occurring at the same time. For example, virtually all the HF reacts with other silica minerals associated with the fluorapatite (silicates, quartz) to form silicon tetrafluoride. These gaseous emissions are recovered as hydroflusilicic acid $(H _2SiF _6)$ in the scrubbing system. Carbonates in the rock also react with sulfuric acid.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

During the manufacturing of single superphosphate, excess silicon combines with:

  1. base

  2. acid

  3. water

  4. none
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reactions occurring  during the production of superphosphate are complex and are usually summarised as follows :

1. $Ca _5(PO _4) _3 F + 5H _2SO _4 \rightarrow 5CaSO _4 + 3H _3PO _4 + HF$
2. $Ca _5(PO _4) _3F + 7H _3 PO _4 + 5H _2O \rightarrow 5Ca(H _2PO _4) _2 H _2O + HF$
These reactions can be combined to give the overall equation :
$2Ca _5(PO _4) _3F + 7H _2SO _4 + 3 H _2O \rightarrow 7CaSO _4 + 3Ca(H _2PO _4) _2 H _2O + 2HF$
There are other reactions occurring at the same time. For example, virtually all the HF reacts with other silica minerals associated with the fluorapatite (silicates, quartz) to form silicon tetrafluoride. These gaseous emissions are recovered as hydroflusilicic acid $(H _2SiF _6)$ in the scrubbing system. Carbonates in the rock also react with sulfuric acid.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

During the manufacturing of superphophates, fluorine and silicon impurities combines with water to form:

  1. silicic acid

  2. fluorosilicic acid

  3. silicon tetrafluoride

  4. form their oxides
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During superphosphate production, silicon tetrafluoride (SiF4) is produced as a byproduct. When this reacts with water, it forms fluorosilicic acid (H2SiF6).

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Which of the following element has $2^{nd} IP<1^{st}IP$?

  1. $Mg$
  2. $Na$
  3. $C$

  4. None
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All three $Mg$, $C$ and $Ne$ have $2nd$ ionisation potential greater than $1st$ ionisation potential. 

This is the general trend shown by most element that $1^{st} IP<2^{nd} IP<3^{rd} IP<$ and so on.
Hence, option D is correct.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Gypsum is a widely occurring mineral. It is the sulphate of calcium with two molecules of water attached. On heating it loses three-quarters of its water and becomes:

  1. baking soda

  2. plaster of Paris

  3. a pearl

  4. an ultramarine
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
It is prepared by heating Gypsum to a temperature of 373K. When gypsum is heated to a temperature of 373K, it loses three-fourths of its water of crystallization and forms Plaster of Paris.
$\underset{\text{Gypsum}}{CaS{O} _{4}.2{H} _{2}O} \xrightarrow[373 K]{\Delta} \underset{\text{Plaster of Paris}}{CaS{O} _{4}.\cfrac{1}{2}{H} _{2}O} + \cfrac{3}{2}{H} _{2}O$