Carbonates and Bi-Carbonates Class 11 Notes | EduRev

Chemistry Class 11

Created by: Mohit Rajpoot

Class 11 : Carbonates and Bi-Carbonates Class 11 Notes | EduRev

The document Carbonates and Bi-Carbonates Class 11 Notes | EduRev is a part of the Class 11 Course Chemistry Class 11.
All you need of Class 11 at this link: Class 11

Carbonates

Sodium Carbonate:

Preparation:

(i)

Carbonates and Bi-Carbonates Class 11 Notes | EduRev 

Carbonates and Bi-Carbonates Class 11 Notes | EduRev

(ii) 

Solvay Process:

NH3 + H2O + CO2  → NH4HCO3

NaCl + NH4HCO3-→ NaHCO3 + NH4Cl

2NaHCO3  → Na2CO3 + H2O + CO2

Properties:

(i)  Anhydrous Na2CO3 is called as soda ash, which does not decompose on heating but melts at 852°C

(ii)  It forms number of hydrates.

Na2CO3. H2O------>. Crystal carbonate <-------Na2CO3 + moisture in air

Na2CO3. 7H2O

Na2CO3.10H2O ----> Washing soda

(iii) Na2CO3 absorbs CO2 yielding sparingly soluble sodium bicarbonate which can be calcined at 250° to get pure sodium carbonate.

Carbonates and Bi-Carbonates Class 11 Notes | EduRev

(iv) It dissolved in acid with effervescence of CO2 and causticised by lime to give caustic soda.

Na2CO3 + HCl > 2NaCl + H2O + CO2

Na2CO3 + Ca(OH)2 2NaOH + CaCO3

Uses : It is widely used in glass making as smelter .


Potassium Carbonate :
By Leblanc process, it can be prepared but by Solvay process it cannot be prepared because KHCO3 is soluble in water.

Properties: It resembles with Na2CO3, m.p. is 900ºC but a mixture of Na2CO3 and K2CO3 melts at 712ºC.

Uses : It is used in glass manufacturing.

Potassium Carbonate :

It occurs in nature as marble, limestone, chalk, coral, calcite etc. It is prepared by dissolving marble or limestone in HCl and removing iron and aluminium present, by precipitating with NH3 and then adding (NH4)2CO3 to the solution.

CaCl2 + (NH4)2CO3 ------>. CaCO3 + 2NH4Cl

Properties:

1. It dissociates above 1000°C as follows:

CaCO3----->CaO + CO2

2. It dissolves in water containing CO2 forming Ca(HCO3)2 but is precipitated from the solution by boiling.

Carbonates and Bi-Carbonates Class 11 Notes | EduRev


Magnesium carbonate :
It occurs in nature as magnesite, isomorphous with calcite. It is obtained as a white precipitated sodium bicarbonate to a solution of a magnesium salt; but only basic carbonate, called magnesia alba, having the approximate composition MgCO3.Mg(OH)2. 3H2O is precipitated.
Properties : Same with CaCO3.


BICARBONATES

Sodium bicarbonates :

Preparation : By absorption of CO2 in Na2CO3 solution.

Carbonates and Bi-Carbonates Class 11 Notes | EduRev

Uses : It is used in medicine and as baking powder.


Potassium bicarbonates: 

Preparation : Same NaHCO

Properties : Same with NaHCO3
But, it is more alkaline and more soluble in water compared to NaHCO3.


Magnesium bicarbonate :

Carbonates and Bi-Carbonates Class 11 Notes | EduRev 


Chlorides:

Sodium Chloride : Prepared from brine containing 25% NaCl.

Properties:
(i) It is non-hygroscopic but the presence of MgCl2 in common salt renders it hygroscopic.
(ii) It is used to prepare freezing mixture in laboratory [Ice-common salt mixture is called freezing mixture and temperature goes down to – 23ºC.]
(iii) For melting ice and snow on road.


Potassium Chloride : It is also occurs in nature as sylvyne (KCl) or carnalite (2KCl . MgCl2 6H2O)

Uses : It is used as fertiliser.


Magnesium Chloride : 

Preparation : By dissolving MgCO3 in dil. HCl.

MgCO+ 2HCl → MgCl2 + H2O + CO2

Properties : 
(i) It crystallises as hexahydrate. MgCl2. 6H2O
(ii) It is deliquescent solid.
(iii) This hydrate undergoes hydrolysis as follows:

Carbonates and Bi-Carbonates Class 11 Notes | EduRev

* Hence, Anhy. MgCl2 cannot be prepared by heating this hydrate.

* * Because of this formation of HCl, Sea water cannot be used in marine boilers which corrodes the iron body.

(iv) Anhydrous MgCl2 can be prepared by heating a double salt like. MgCl2 . NH4Cl . 6H2O as follows:
Carbonates and Bi-Carbonates Class 11 Notes | EduRev

Sorel Cement: It is a mixture of MgO and MgCl2 (paste like) which set to hard mass on standing. This is used in dental filling, flooring etc.


Calcium chloroide :

(i)  It is the by-product in solvay process.

(ii)  It may also be prepared by dissolving the carbonate in HCl .

CaCO3 + 2HCl → CaCl2 + H2O + CO2

 

Properties :

(i) It is deliquescent crystals.

(ii) It gets hydrolysed like MgCl2 hence anhydrous CaCl2 cannot be prepared.

CaCl2 + H2O Carbonates and Bi-Carbonates Class 11 Notes | EduRev CaO + 2HCl

Hence, anhy. CaCl2 is prepared by heating CaCl2.6H2O in a current of HCl (dry)

(iii) Anhy. CaCl2 is used in drying gases and organic compounds but not NH3 or alcohol due to the formation of CaCl2. 8NH3 and CaCl2. 4C2H5OH.


Sodium sulphate:

Preparation :
It is formed in the 1st step of Leblanc process by heating common salt with sulphuric acid.

2NaCl + H2SO4 → Na2SO4 + 2HCl

Thus the salt cake formed is crystallised out from its aqueous solution as Na2SO4.10H2O. This called as Glauber's salt.

** One interesting feature of the solubility of Glauber's salt is: when crystallised at below

32.4ºC, then Na2SO4. 10H2O is obtained but above 32.4ºC, Na2SO4 (anhy.) comes out.


Properties : It is reduced to Na2S when fused with carbon.

Na2SO4 + 4C → Na2S + 4CO

Uses : It is used in medicine.


Potassium Sulphate :

It occurs in sulphate of potash beds as schonite K2SO4. MgSO4.6H2O and Kainite, KCl .MgSO4.3H2O from which it is obtained by solution in water and crystallisation. It separates from the solution as anhydrous crystals whereas Na2SO4 comes as decahydrate.

Uses : It is used to prepare alum.


Magnesium Sulphate :

Preparation :
(i) It is obtained by dissolving Kieserite, MgSO4.H2O in boiling water and then crystallising the solution as a heptahydrate. i.e. MgSO4. 7H2O. It is called as Epsom salt.

(ii) It is also obtained by dissolving magnesite in hot dil. H2SO4.
MgCO3 + H2SO4 → MgSO4 + H2O + CO2

(iii) Or by dissolving dolomite (CaCO3, MgCO3) in hot dil. H2SO4 and removing the insoluble CaSO4 by filtration.

(iv) It is isomorphous with FeSO4.7H2O, ZnSO4.7H2O

Calcium Sulphate : It occurs as anhydrite CaSO4 and as the dihydrate CaSO4. 2H2O, gypsum, alabaster or satin-spar.

Properties :

(i)  Carbonates and Bi-Carbonates Class 11 Notes | EduRev

(ii) Solubility of CaSO4 at first increases upto a certain point and then decreases with rise of temperature.

(iii) Plaster of Paris is used in mould making due to its porous body.

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