Sodium Carbonate (Washing soda) (Na2CO3

✅Sodium Carbonate (Washing soda) (Na2CO3): 

a) Preparation:  

Solvay process:

Carbon dioxide gas is bubbled through a brine solution saturated with ammonia and itresults in the formation of sodium hydrogen carbonate.

NH3 + H2O + CO2 → NH4HCO3

NaCI + NH4HCO3 → NaHCO3 + NH4CI         

Sodium hydrogen carbonate so formed precipitates out because of the common ion effect caused due to the presence of excess of NaCl. The precipitated NaHCO3 is filtered off and then ignited to get Na2CO3.

2NaHCO3 → Na2CO3 + CO2 + H2O

b) Properties

1.  The aqueous solution absorbs CO2 yielding sparingly soluble sodium bicarbonate.

 Na2CO3 + H2O + CO2 → 2NaHCO­3

 2. dissolves in acids with an effervescence of carbondioxide and is causticised by lime to give caustic soda.

Na2CO3 + 2HCl →2NaCl + H2O + CO2

Na2CO3 + Ca(OH)2 → 2NaOH + CaCO3

3.  Fusion with silica, sodium carbonate yields sodium silicate.

Na2CO3 + SiO2 → Na2SiO3 + CO­2

4. Hydrolysis – being a salt of a strong base (NaOH) and weak acid (H2CO3), when dissolved in water sodium carbonate. Undergoes hydrolysis to form an alkaline solution

Na2CO3 + 2H2O→ H2CO3 + 2NaOH

c) Uses

It is used for softening hard water.

A mixture of sodium carbonate & potassium carbonate is used as fusion mixture.

As an important laboratory reagent both in qualitative and quantitative analysis.

It is used in paper, paints and textile industries.

It is used for washing purposes in laundry.

It is used in the manufacture of glass, borax, soap and caustic soda.

Alkali Earth Metals (Group II elements of modern periodic table):

Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba) and Radium (Ra).

Physical Properties of Alkali Earth Metals:

1. Alkali earth metals are almost similar in properties to the corresponding alkali metals.

Higher melting points than alkali metals

Higher boiling points alkali metals

Higher densities alkali metals

Harder than the corresponding alkali metals

2. Atomic and ionic radii

The atomic radii as well as ionic radii of the members of the family are smaller than the corresponding members of alkali metals.

3. Ionization energy: The alkaline earth metals owing to their large size of atoms have fairly low values of ionization energies as compared to the p – block elements. However with in the group, the ionization energy decreases as the atomic number increases. It is because of increase in atomic size due to addition of new shells and increase in the magnitude of screening effect of the electrons in inner shells. Because their (IE)1 is larger than that of their alkali metal neighbours, the group IIA metals trend to the some what less reactive than alkali metals. The general reactivity trend is Ba > Sr > Ca > Mg > Be.

4. Oxidation state: The alkaline earth metal have two electrons in their valence shell and by losing these electrons, these atoms acquire the stable noble gas configuration. Thus, unlike alkali metals, the alkaline earth metals exhibit +2 oxidation state in their compounds.