Q.15 When dissolved in water, the number of H+ ions released from a molecule of H3BO3 is __________.
SEO-Optimized Introduction
Acid strength and the number of hydrogen ions released in water are common concepts tested in chemistry examinations. A frequently asked conceptual question is: When dissolved in water, how many H⁺ ions are released from a molecule of H₃BO₃? Although boric acid contains three hydrogen atoms, its behavior in aqueous solution is unique. Let’s understand this concept clearly with proper reasoning.
Understanding the Nature of Boric Acid (H₃BO₃)
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Chemical name: Boric acid
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Molecular formula: H₃BO₃
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Structure: Contains three –OH groups bonded to boron
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Boron is electron-deficient (only 6 valence electrons)
Important Concept
Boric acid is not a proton donor acid.
It acts as a Lewis acid, not a Brønsted acid.
How H₃BO₃ Behaves in Water
Boric acid does not directly release H⁺ ions.
Instead, it accepts OH⁻ ions from water, increasing H⁺ concentration indirectly.
Reaction in water:
H3BO3+2H2O→B(OH)4−+H3O+\text{H}_3\text{BO}_3 + 2\text{H}_2\text{O} \rightarrow \text{B(OH)}_4^- + \text{H}_3\text{O}^+
✔ Only one H⁺ ion is produced per molecule of H₃BO₃
✔ Hence, boric acid behaves as a monobasic acid
Option-Wise Explanation
Option (A): 1
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H₃BO₃ increases H⁺ concentration by forming one hydronium ion
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Acts as a monobasic acid
Correct
Option (B): 2
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Would require release of two protons
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H₃BO₃ does not donate protons directly
Incorrect
Option (C): 3
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Though formula has three hydrogens, none are ionizable
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No direct proton donation
Incorrect
Option (D): 0
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H⁺ ions are produced indirectly
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Solution is acidic
Incorrect
Final Answer
Correct Option: (A) 1
Key Takeaways
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Boric acid is a Lewis acid
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Does not donate protons directly
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Accepts OH⁻ from water
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Releases only one H⁺ ion indirectly
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Hence, H₃BO₃ is monobasic
Exam Tip
Do not judge basicity by counting hydrogen atoms.
Always analyze acid behavior in water.
