Sodium hydrogen carbonate (NaHCO₃), commonly known as baking soda, is classified as a basic salt because it produces an alkaline (basic) solution when dissolved in water, with pH approximately 8.3. Although NaHCO₃ contains the hydrogen carbonate ion (HCO₃⁻) which can act as both an acid and a base, the hydrolysis of HCO₃⁻ in water releases OH⁻ ions more than H⁺ ions, making the solution alkaline.
NaHCO₃ (sodium hydrogen carbonate / baking soda) is a basic salt — gives alkaline solution (pH ≈ 8.3).
HCO₃⁻ hydrolyses in water: HCO₃⁻ + H₂O ⇌ H₂CO₃ + OH⁻ → more OH⁻ released.
Formed from strong base (NaOH) + weak acid (H₂CO₃) → alkaline salt.
Decomposition on heating: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂↑
Reacts with acids: NaHCO₃ + HCl → NaCl + H₂O + CO₂↑
Used as baking powder, antacid, fire extinguisher, and medicine.
Na₂CO₃ (washing soda) is more strongly basic than NaHCO₃.
NaHCO₃ is an amphoteric ion (HCO₃⁻ can act as both acid and base) but the net effect is basic.
NaHCO₃ is formed by partial neutralisation of carbonic acid (H₂CO₃) with sodium hydroxide (NaOH): H₂CO₃ + NaOH → NaHCO₃ + H₂O
In water, NaHCO₃ dissociates completely: NaHCO₃ → Na⁺ + HCO₃⁻
The HCO₃⁻ ion can act as both a weak acid and a weak base: As an acid: HCO₃⁻ ⇌ H⁺ + CO₃²⁻ (Ka₂ = 4.7 × 10⁻¹¹) As a base: HCO₃⁻ + H₂O ⇌ H₂CO₃ + OH⁻ (Kb = 2.4 × 10⁻⁸)
Since Kb > Ka₂ for HCO₃⁻, hydrolysis (base reaction) dominates over ionisation (acid reaction): → More OH⁻ is produced than H⁺ → The solution is alkaline (basic) → pH of NaHCO₃ solution ≈ 8.3
Conclusion: NaHCO₃ is a basic salt because its aqueous solution is alkaline.
In Indian school chemistry (CBSE/NCERT):
NaHCO₃ is called a basic salt because: • It is a salt that gives an alkaline (basic) solution in water • It is formed from a strong base (NaOH) and a weak acid (H₂CO₃) • Salts of strong base + weak acid → alkaline solution
Note on terminology: In some classification systems: • NaHCO₃ is called an acidic salt (because the H in HCO₃⁻ makes it an acid salt structurally) • But in terms of its solution, it is alkaline/basic
Standard CBSE classification: NaHCO₃ is a basic salt (gives alkaline solution).
Comparison: • Na₂CO₃ (sodium carbonate / washing soda): stronger basic salt, pH ~11 • NaHCO₃ (sodium bicarbonate / baking soda): mildly basic, pH ~8.3 • NaCl (common salt): neutral, pH = 7 (strong acid + strong base)
Physical properties: • White crystalline powder • Mild salty, alkaline taste • Decomposes on heating: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂↑ (above 50°C)
Chemical reactions: • With acid: NaHCO₃ + HCl → NaCl + H₂O + CO₂↑ (reacts with acids — useful for antacid action) • With base: NaHCO₃ + NaOH → Na₂CO₃ + H₂O
Uses of sodium hydrogen carbonate:
Sodium hydrogen carbonate (NaHCO₃) is called a basic salt because it gives an alkaline (basic) solution in water (pH ≈ 8.3). When dissolved in water, the HCO₃⁻ ion hydrolyses to form H₂CO₃ and OH⁻ ions. Since more OH⁻ is released than H⁺, the solution is alkaline.
The pH of a sodium hydrogen carbonate (NaHCO₃) solution is approximately 8.3. This is slightly alkaline (basic), confirming that NaHCO₃ is a basic salt.
NaHCO₃ decomposes on heating above 50°C: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂↑. This is why baking soda makes baked goods rise — it releases CO₂ when heated in the oven.
NaHCO₃ is alkaline in nature. It reacts with excess hydrochloric acid (HCl) in the stomach: NaHCO₃ + HCl → NaCl + H₂O + CO₂. This neutralises the excess acid and relieves acidity. The CO₂ produced causes mild belching.
NaHCO₃ is classified as a basic salt in CBSE/school chemistry because its aqueous solution is alkaline (pH > 7). Though the HCO₃⁻ ion is structurally an 'acid salt' (still contains H), the solution behaves as basic due to the hydrolysis of HCO₃⁻ producing OH⁻ ions.
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