Tag: chemistry

Questions Related to chemistry

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

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

  1. Third

  2. Second

  3. First

  4. Fourth

Show answer
Correct Option: B
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 $B$

Sorel cement is the mixture of:

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

  1. $CaCO _3+H _2O$

  2. $MgCl _2+MgO$

  3. $BaSO _4+CO _2$

  4. $MgO+Na _2HPO _4$

Show answer
Correct Option: B
Explanation:

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

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

The formula for the most abundant mineral in phosphate rock is: 

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

  1. $Ca _5(PO _4) _3F$

  2. $Ca _5(PO _4) _2F _4$

  3. $Ca _4(PO _4) _2F _2$

  4. $Ca _6(PO _4) _3F _3$

Show answer
Correct Option: A
Explanation:

Most abundant mineral of phosphate rock is Fluorapetite, which has the formula of $Ca _5(PO _4) _3F$.

The most abundant mineral in Phosphate rock is: 

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

  1. Flourspar

  2. Phosphane

  3. Flourapetite

  4. Phosphide

Show answer
Correct Option: C
Explanation:

Most abundant mineral of phosphate rock is Fluorapetite, which has the formula of $Ca _5(PO _4) _3F$.

Chlorophyll is a ______ complex.

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

  1. Magnesium - Porphyrin

  2. Iron - Porphyrin

  3. Copper - Porphyrin

  4. Nickel - Porphyrin

Show answer
Correct Option: A
Explanation:

Chlorophyll is a magnesium - porphyrin complex.
Chlorophyll is the main pigment for the absorption of light in plants and is useful during photosynthesis.

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

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

  1. silicates

  2. silicic acid

  3. silanes

  4. hydride of silicon

Show answer
Correct Option: B
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.

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

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

  1. base

  2. acid

  3. water

  4. none

Show answer
Correct Option: B
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.

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

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

  1. silicic acid

  2. fluorosilicic acid

  3. silicon tetrafluoride

  4. form their oxides

Show answer
Correct Option: B

The impurities present in the phosphate rock is/are:

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

  1. chlorine

  2. fluorine

  3. silicon

  4. carbon

Show answer
Correct Option: B,C
Explanation:

The impurities present in the phosphate rock are silicon and flourine. If phosphate rock is digested in phosphoric acid, silicon dioxide and hydrogen flouride are formed. 

Which of the following is isomorphous with $MgSO _4\cdot 7H _2O$ ?

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

  1. Green vitriol

  2. Blue vitriol

  3. Red vitriol

  4. Vitriol of mass

Show answer
Correct Option: A
Explanation:

Green vitroil is isomorphous with $MgSO _4.7H _2O$

 $MgSO _4.7H _2O$ (epsom salt)
 $FeSO _4.7H _2O$ (green vitriol)
these two are isomorphous .