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Why are ionic compounds generally soluble in water but insoluble in organic solvents like petrol and kerosene?
Water is a polar solvent and forms ion-dipole interactions, whereas organic solvents are non-polar.
Ionic compounds have low melting points.
Organic solvents react chemically with ionic compounds.
Ions are destroyed in organic solvents.
Water is a polar solvent and forms ion-dipole interactions, whereas organic solvents are non-polar.
Ionic compounds consist of charged ions held together by strong electrostatic forces. They dissolve in water because water is a polar solvent that stabilizes these ions through ion-dipole interactions, while non-polar organic solvents like petrol cannot overcome the lattice energy of the ionic crystal.
Ionic compounds consist of charged ions held together by strong electrostatic forces. They dissolve in water because water is a polar solvent that stabilizes these ions through ion-dipole interactions, while non-polar organic solvents like petrol cannot overcome the lattice energy of the ionic crystal.
Think of salt as a magnet-locked brick; water acts like many tiny, powerful magnets that pull the bricks apart, while oil is like a neutral block of wax that cannot grab the magnet-brick to pull it apart.
Like dissolves like (Polar dissolves Polar, Non-polar dissolves Non-polar).
FcтАЛ=r2kq1тАЛq2тАЛтАЛ тАФ Coulomb's Law defining the electrostatic force between ions in a vacuum.
╬ФHsolnтАЛ=╬ФHlatticeтАЛ+╬ФHhydrationтАЛ тАФ Heat of solution calculation based on lattice and hydration energies.
The dissolution follows the principle of 'like dissolves like'. Water, having a high dielectric constant, reduces the electrostatic force of attraction between ions (F=4╧А╧╡0тАЛ1тАЛr2q1тАЛq2тАЛтАЛ) via hydration energy. Organic solvents lack this polarity and cannot effectively interact with the charged ions, leaving the crystalline lattice intact.
Ionic compounds possess high lattice energy.
Water has a high dielectric constant (approx 80) which helps break ionic bonds.
Organic solvents do not have a dipole moment sufficient to solvate ions.
The process of ion-dipole interaction is exothermic, providing the energy for solubility.
Predictability of solubility based on polarity.
Ionic compounds are typically non-conductors in solid state but conductive in aqueous solutions.
Electrolysis of molten or aqueous salts.
Separation techniques using differential solubility.
| Feature | Water | Organic Solvent |
|---|---|---|
Solvent Polarity | Polar (e.g., Water) | Non-polar (e.g., Petrol) |
Effect on Ions | Hydrates and separates ions | Fails to separate ions |
Dielectric constant of water is 78.4 at 25┬░C.
Option B is incorrect because ionic compounds actually have very high melting points due to strong electrostatic forces.
Option C is incorrect as ionic compounds are generally stable and do not react with neutral hydrocarbons.
Option D is incorrect; ions are not destroyed, they are simply not dissociated in non-polar solvents.
A is correct тАФ Water is a polar solvent and forms ion-dipole interactions, whereas organic solvents are non-polar.
Always remember the rule 'Like dissolves like'тАФit is a fundamental concept appearing in chemistry questions across various competitive exams including SSC, RRB, and UPSC.
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