Is NH3 is a weak base and H2CO3 is a strong acid?
The correct answer and explanation is:
Correct Answer:
NH₃ (ammonia) is a weak base, and H₂CO₃ (carbonic acid) is a weak acid.
Explanation:
Ammonia (NH₃) is classified as a weak base. This is because it does not completely dissociate or accept protons (H⁺ ions) when dissolved in water. Instead, it establishes an equilibrium with water molecules:
NH₃ + H₂O ⇌ NH₄⁺ + OH⁻
In this reaction, only a small percentage of ammonia molecules react with water to form ammonium ions (NH₄⁺) and hydroxide ions (OH⁻). Since this reaction does not go to completion and the base does not fully ionize, ammonia is considered a weak base.
On the other hand, H₂CO₃ (carbonic acid) is also a weak acid, not a strong acid. When carbonic acid dissolves in water, it partially dissociates into hydrogen ions and bicarbonate ions:
H₂CO₃ ⇌ H⁺ + HCO₃⁻
This dissociation also exists in equilibrium and does not go to completion, which is characteristic of weak acids. Furthermore, H₂CO₃ can undergo a second, weaker dissociation:
HCO₃⁻ ⇌ H⁺ + CO₃²⁻
Again, both dissociation steps are incomplete, confirming the weak acidic nature of carbonic acid. In contrast, strong acids, like hydrochloric acid (HCl), sulfuric acid (H₂SO₄), or nitric acid (HNO₃), dissociate completely in solution.
Therefore, both NH₃ and H₂CO₃ are weak in their respective categories. The statement that NH₃ is a weak base is true. However, the claim that H₂CO₃ is a strong acid is false. Understanding acid and base strength is important for predicting reaction direction and the pH of solutions.