Question

can anyone give the solubility order for alkali metal chlorides and carbonates? '

Answer 1

Hydroxides of Alkali Earth MetalsThe hydroxides of Ca, Sr & Ba are obtained either by treating the metal with cold water or by reacting the corresponding oxides with water. The reaction of these oxides with H2O is also sometimes called as slaking.M + 2H2O  →  M (OH)2 + H2 ( M = Ca, Sr, Ba)MO + H2O → M (OH)2 (M = Ca, Sr, Ba)                            Be(OH)2 and Mg(OH)2 being insoluble are obtained from suitable metal ion solutions by precipitation with OH- ions.BeCI2 + 2NaOH → Be (OH)2 ↓ + 2NaCI               MgSO4 + 2NaOH → Mg (OH)2 ↓ + Na2SO4              Properties of Hydroxides of Alkali Earth Metals(i)  Basic Character All the alkaline earth metal hydroxides are bases except Be (OH)2 which is amphoteric. This basic strength increases as we move down the group. This is because of increase in size which results in decrease of ionization energy which weakens the strength of M – O bonds in MOH and thus increases the basic strength. However, these hydroxides are less basic than the corresponding alkali metal hydroxides because of higher ionization energies, smaller ionic sizes and greater lattice energies.(ii) Solubility in WaterAlkaline earth metals hydroxides are less soluble in water as compared to alkali metals.The solubility of the alkaline earth metal hydroxides in water increases with increase in atomic number down the group. This is due to the fact that the lattice energy decreases down the group due to increase in size of the alkaline earth metals cation whereas the hydration energy of the cation remains almost unchanged. The resultant of two effects i.e.ΔHsolution = ΔHlattice  - ΔHHydration Becomes more negative as we move from Be(OH)2 to Ba(OH)2 which accounts for increase in solubility.Halides of Alkali Earth MetalsThe alkaline earth metals combine directly with halogen at appropriate temperature forming halides MX2.These halides can also be prepared by the action of halogen acids (HX) on metals, metals oxides, hydroxides and carbonates.M + 2HX → MX2 + H2MO + 2HX → MX2 + H2O      M (OH)2 + 2HX → MX2 + 2H2O     MCO3 + 2HX → MX2 + H2O + CO2       Properties of Halides of Alkali Earth MetalsAll beryllium halides are essentially covalent and are soluble in organic solvents. They are hydroscopic and fume in air due to hydrolysis. On hydrolysis, they produce acidic solution.
BeCI2 + 2H2O → Be (OH)2 + 2HCI       The halides of all other alkaline earth metals are ionic. Their ionic character, however increases as the size of the metal ion increase.Except BeCl2 all other chlorides of group 2 form hydrates but their tendency to form hydrates decreases for eg –
MgCl2.6H2O, CaCl2.6H2O.The hydrated chloride, bromides and iodides of Ca, Sr and Ba can be dehydrated on heating but those of Be and Mg undergo hydrolysis.BeF2 is very soluble in water due to the high hydration energy of the small Be+2ion. The other fluorides (MgF2, CaF2, SrF2 and BaF2) are almost insoluble in water. Since on descending the group lattice energy decreases more rapidly than the hydration energy. Therefore whatever little solubility these fluorides have that increase down the group.The chlorides, bromides and iodides of all other elements i.e. Mg, Ca, Sr, Ba are ionic have much lower melting points than the fluorides and are readily soluble in water. The solubility decreases some what with increasing atomic number.Except of BeCl2 and MgCl2, the other chlorides of alkaline earth metals impart characteristics colour to flame.
CaCl2 = Brick red colour
SrCl2 = Crimson colour
BaCl2 = Grassy green colourUsesCalcium fluoride or fluorospar (CaF2) is by far the most important of all the fluorides of the alkaline earth metals since it is the only large scale source of fluorine.CaCl2 is widely used for melting ice on roads, particularly in very cold countries because 30% eutectic mixture of CaCl2/ice freezes at 218 K as compared to NaCl /ice at 255K.CaCl2 is also used as a desiccant (drying agent) in the laboratory.Anhydrous MgCl2 is used in the electrolytic extraction of magnesium.Solubility and thermal stability of oxo saltsThe salts containing one or more atoms of oxygen such as oxides, hydroxides, carbonates, bicarbonates, nitrites, nitrates, sulphates, oxalates and phosphates are called oxo salts.

Answer 2

Explanation:

As elements of alkali group are lithium, sodium, potassium, rubidium, cesium and francium.

As it is known that when we move down the group in a periodic table there will be increase in the size of elements.

So, for alkali metal chlorides, anion that is chloride here is fixed. So, greater will be the difference in size of combining atoms greater will be the solubility.

On the other hand, according to Fajan's rule smaller is the size of cation and larger the size of anion will lead to increase in covalent character. As a result, there will be decrease in solubility.

Since, carbonate ion is fixed for all the metal carbonates. Hence, size of cation will decide the solubility then. As smaller is the size of cation lesser will be the solubility.