Compare the solubility and thermal stability of the following compounds of the alkali metals with those of the alkaline earth metals.

(a) Nitrates

(b) Carbonates

(c) Sulphates.

Asked by Pragya Singh | 11 months ago |  62

##### Solution :-

(a) Nitrates

Thermal stability

Except LiNO3, the nitrates of alkali metals gets decomposed while heating strong which results in the formation of nitrites.

$$2KNO_{3}\rightarrow 2KNO_{2}+O_{2(g)}$$

LiNO3, on decomposition, gives oxide.

$$2LiNO_{3}\rightarrow Li_{2}O+2NO_{2(g)}+O_{2(g)}$$

Like lithium nitrate, alkaline earth metal nitrates also decomposes to give oxides.

$$2Ca(NO_{3})\rightarrow 2CaO+4NO_{2(g)}+O_{2(g)}$$

Solubility

Nitrates of both group 1 and group 2 metals are soluble in water.

(b) Carbonates

Thermal stability

The alkali metals carbonates are very stable to heat. But carbonates of lithium decomposes and results in the formation of lithium oxide while heating. The carbonates of alkaline earth metals also decompose which results in the formation of carbon dioxide and oxide while heating.

$$Na_{2}CO_{3}\rightarrow No\; Effect$$

$$Li_{2}CO_{3}\rightarrow Li_{2}O+CO_{2}$$

$$MgCO_{3}\rightarrow MgO+CO_{2}$$

Solubility

Exception of  Li2 CO3, the carbonates of alkali metals are soluble in water and also while we move down the group, the solubility increases. Carbonates of alkaline earth metals are insoluble in water.

(c) Sulphates

Thermal stability

Sulphates of both group 1 and group 2 metals are stable towards heat.

Solubility

Sulphates of alkali metals are soluble in water. But the sulphates of alkaline earth metals shows various activities,

CaSO4 Sparingly soluble

BaSO4 Insoluble

BeSO4 Fairly soluble

SrSO4 Insoluble

MgSO4 Soluble

Answered by Abhisek | 11 months ago

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