Just have a simple question, is the aqueous solutions for the salts Ba(NO2)2 and K2SO3 acidic, basic, or neutral?
The correct answer and explanation is:
Correct Answer:
- Ba(NO₂)₂ (Barium nitrite): Basic
- K₂SO₃ (Potassium sulfite): Basic
Explanation (300 words):
To determine whether an aqueous salt solution is acidic, basic, or neutral, it is important to examine the ions formed when the salt dissolves in water and whether these ions undergo hydrolysis. Salts are typically made from the neutralization of acids and bases. The pH of the resulting solution depends on the strength of the acid and base from which the salt is derived.
1. Ba(NO₂)₂ – Barium Nitrite:
This salt dissociates in water into Ba²⁺ and NO₂⁻ ions. Barium (Ba²⁺) is the cation from a strong base (Ba(OH)₂), and nitrite (NO₂⁻) is the conjugate base of a weak acid (HNO₂ – nitrous acid). Since Ba²⁺ is a spectator ion and does not hydrolyze, and NO₂⁻ is the conjugate base of a weak acid, it hydrolyzes with water to form OH⁻ (hydroxide ions). This leads to a basic solution.
The hydrolysis reaction is:
NO₂⁻ + H₂O ⇌ HNO₂ + OH⁻
The formation of OH⁻ raises the pH, making the solution basic.
2. K₂SO₃ – Potassium Sulfite:
This salt dissociates into 2 K⁺ and SO₃²⁻ ions. Potassium (K⁺) comes from a strong base (KOH), so it is a spectator ion. Sulfite (SO₃²⁻) is the conjugate base of a weak acid (H₂SO₃ – sulfurous acid). Like nitrite, sulfite undergoes hydrolysis and produces OH⁻ in the process.
The hydrolysis reaction is:
SO₃²⁻ + H₂O ⇌ HSO₃⁻ + OH⁻
This reaction results in an increased concentration of hydroxide ions, making the solution basic.
Conclusion:
Both Ba(NO₂)₂ and K₂SO₃ form basic solutions in water because their anions (NO₂⁻ and SO₃²⁻) are conjugate bases of weak acids and hydrolyze to produce hydroxide ions. Their cations are from strong bases and do not affect the pH.