Saved Bookmarks
| 1. |
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. |
|
Answer» Solution : (a) Nitrates : (i) Thermal stability : Nitrates of alkali metals, except `LiNO_(3)`, decompose on strong heating to form nitrites. `2KNO_(3(s)) to 2KNO-(2(s)) + O_(2(g))` `LiNO_(3)`on decomposition gives OXIDE. ` 2LiNO_(3(s)) overset(Delta)to 2CaO_((s)) +4NO_(2(s))+O_(2(g))` As we move down group-1 and group-2, the thermal stability of nitrate increases. (II) Solubility : Nitrates of both group-1 and group-2 metals are soluble in water. (b) CARBONATES : (i) Thermal stability: The carbonates of alkali metals are stable towards heat. However, carbonate of lithium, when heated, decomposes to form lithium oxide. The carbonates of alkaline earth metals also decompose on heating to form oxide and carbon dioxide. `Na_(2)CO_(3) overset(Delta)to ` No reaction. `Li_(2)CO_(3) overset(Delta)to Li_(2)O+CO_(2)` `MgCO_(3) overset(Delta)to MgO+CO_(2)` (ii) Solubility : Carbonates of alkali metals are soluble in water with the exception of `Li_(2)C0_(3)`. Also, the solubility increases as we move down the group. Carbonates of alkaline earth metals are insoluble in water. (c) Sulphates : (i) Thermal stability : Sulphates of both group-1 and group-2 metals are stable towards heat. (ii) Solubility : Sulphates of alkali metals are soluble in water. However, sulphates of alkaline earth metals show VARIED trends. `BeSO_(4)` - Fairly soluble `MgSO_(4)` - Soluble `CaSO_(4)` - Sparingly soluble `SnSO_(4)` - Insoluble `BaSO_(4)` - Insoluble In other words, while moving down the alkaline earth metals, the solubility of their sulphates decreases. |
|