The molar solubility of barium sulfite (BaSO₃) in a water solution is approximately 1.0 x 10⁻⁴ mol/L.
Barium sulfite is known to have very low solubility in water. Solubility is a measure of the maximum amount of a substance that will dissolve in a given amount of solvent at a specific temperature to form a saturated solution. Molar solubility specifically refers to the concentration of the dissolved solute in moles per liter (mol/L) of the saturated solution.
According to available data, which includes the reference provided:
- The solubility of barium sulfite in water at 16°C is cited as 1 part of BaSO₃ per 46,000 parts of water.
- This ratio is equivalent to 2.2 x 10⁻² grams of BaSO₃ per kilogram of water.
- Crucially, this value is also explicitly stated as a molal concentration: m(BaSO₃) = 1.0 x 10⁻⁴ mol kg⁻¹.
Understanding the Solubility Value
The reference provides the solubility as a molal concentration (m), expressed in moles of solute per kilogram of solvent (mol/kg). The question asks for molar solubility (M), expressed in moles of solute per liter of solution (mol/L).
For very dilute aqueous solutions, like that of slightly soluble salts such as barium sulfite, the molal concentration is numerically very close to the molar concentration. This is because:
- The mass of the dissolved solute is negligible compared to the mass of the water (solvent).
- The density of the dilute solution is very close to the density of pure water, which is approximately 1 kg/L, especially near room temperature (16°C is close to this range).
Therefore, 1 kilogram of water corresponds very closely to 1 liter of solution volume in this context.
Reference Information:
| Property | Value | Units | Conditions |
|---|---|---|---|
| Solubility (parts ratio) | 1 part BaSO₃ per 46000 | parts water | 16°C |
| Solubility (mass/mass) | 2.2 x 10⁻² | g BaSO₃/kg H₂O | 16°C |
| Solubility (molal concentration) | 1.0 x 10⁻⁴ | mol kg⁻¹ | 16°C |
(Information derived from the provided reference)
Based on the molal solubility value from the reference (1.0 x 10⁻⁴ mol kg⁻¹) and the approximation for dilute solutions, the molar solubility is approximately 1.0 x 10⁻⁴ mol/L.
Practical Implications
The extremely low molar solubility (on the order of 10⁻⁴ M) indicates that barium sulfite is a sparingly soluble salt.
- Precipitation: If barium ions (Ba²⁺) and sulfite ions (SO₃²⁻) are present in a solution and their concentrations exceed the solubility limit, barium sulfite will precipitate out of the solution.
- Environmental Fate: Due to its low solubility, BaSO₃ that forms or is released into the environment is likely to exist as a solid rather than being dissolved in water.
- Chemical Reactions: The low concentration of Ba²⁺ and SO₃²⁻ ions in equilibrium with the solid impacts the extent of any reactions involving these ions in saturated solutions.
Understanding the exact molar solubility at a given temperature is crucial for chemical calculations involving precipitation, dissolution, and equilibrium reactions of barium sulfite.
