Sodium sulphate is soluble in water but barium sulphate is insoluble b...
Sodium sulphate (Na2SO4) and barium sulphate (BaSO4) are both compounds that contain sulphate ions (SO4^2-) and metal cations (Na+ and Ba^2+). However, they have different solubilities in water. Sodium sulphate is soluble in water, while barium sulphate is insoluble. This difference in solubility can be explained by considering the hydration energy and lattice energy of the compounds.
1. The Hydration Energy of Na2SO4 is More Than its Lattice Energy:
- When sodium sulphate dissolves in water, the water molecules surround and interact with the sodium and sulphate ions. This process is called hydration.
- The hydration of sodium sulphate is an exothermic process, meaning that energy is released when water molecules surround the ions.
- The hydration energy of sodium sulphate is greater than its lattice energy, which is the energy required to separate the ions in the solid state.
- As a result, the energy released during hydration is sufficient to overcome the lattice energy, allowing sodium sulphate to dissolve in water.
2. The Lattice Energy of BaSO4 is More Than its Hydration Energy:
- On the other hand, barium sulphate has a higher lattice energy compared to its hydration energy.
- The lattice energy of a compound is the energy required to separate the ions in the solid state.
- The hydration energy of barium sulphate is not sufficient to overcome the high lattice energy.
- As a result, barium sulphate does not dissolve in water and remains in the solid state as an insoluble compound.
3. Both Factors Affect Solubility:
- In summary, solubility is influenced by both the hydration energy and lattice energy of a compound.
- If the hydration energy is greater than the lattice energy, the compound will dissolve in water (like sodium sulphate).
- If the lattice energy is greater than the hydration energy, the compound will not dissolve in water and remain insoluble (like barium sulphate).
In conclusion, the solubility of sodium sulphate and barium sulphate in water can be explained by considering the relative magnitudes of their hydration energies and lattice energies. Sodium sulphate is soluble because its hydration energy is greater than its lattice energy, while barium sulphate is insoluble because its lattice energy is greater than its hydration energy.
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