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

Which ionisation energy of alkaline earth metal is less than that of alkali metals?

  1. Third

  2. Second

  3. First

  4. Fourth
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The second ionisation energy of alkaline earth metal is less than that of alkali earth metals.
The 2nd electron in case of alkali metal is to be removed from a cation (unipostive ion) which has already acquired a noble gas configuration whereas, in case of alkaline earth metals, the second electron is to be removed from a cation which is yet to acquire the stable noble gas configuration. Therefore, removal of 2nd electron in case of alkaline earth metals requires much less energy than that in the case of alkali metals.

Hence, the correct option is $B$
Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Sorel cement is the mixture of:

  1. $CaCO _3+H _2O$
  2. $MgCl _2+MgO$
  3. $BaSO _4+CO _2$
  4. $MgO+Na _2HPO _4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Sorel cement is a mixture of magnesium chloride and magnesium oxide.

$5MgO+MgCl _2+13H _2O \rightarrow MgCl _2.5Mg(OH) _2.H _2O$
$3MgO+MgCl _2+11H _2O \rightarrow MgCl _2.3Mg(OH) _2.H _2O$

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).