Rank the given compounds based on their relative Bronsted acidities. strongest Bronsted acid weakest Bronsted acid H – CH_3 H – NH_2 H – SH H – F H – I
The Correct Answer and Explanation is :
Rank of Compounds Based on Relative Brønsted Acidity:
H-I > H-F > H-SH > H-NH₂ > H-CH₃
Explanation:
1. Definition of Brønsted Acidity: Brønsted acidity refers to the tendency of a compound to donate a proton (H⁺). A stronger Brønsted acid dissociates more readily in solution, yielding a higher concentration of H⁺ ions.
2. Factors Influencing Acidity:
- Bond Strength: The strength of the bond between hydrogen and the attached atom significantly affects acidity. A weaker bond allows easier release of H⁺.
- Electronegativity: Higher electronegativity stabilizes the conjugate base by better accommodating the negative charge.
- Polarizability: Larger atoms better stabilize the negative charge due to their greater polarizability.
Compound Analysis:
- H-I (Strongest Acid):
- Bond Strength: Iodine is a large atom, resulting in a weak H-I bond.
- Polarizability: The conjugate base (I⁻) is highly stable due to its large size and ability to delocalize charge.
- Conclusion: H-I is the strongest acid.
- H-F:
- Electronegativity: Fluorine is the most electronegative element, stabilizing the conjugate base (F⁻).
- Bond Strength: The H-F bond is very strong, which slightly reduces acidity compared to H-I.
- Conclusion: H-F is the second strongest acid.
- H-SH:
- Polarizability: Sulfur, being larger than oxygen, stabilizes the conjugate base (SH⁻) better than H-NH₂.
- Conclusion: Moderate acidity.
- H-NH₂:
- Electronegativity: Nitrogen is less electronegative than oxygen or fluorine, making NH₂⁻ less stable.
- Conclusion: Weak acid.
- H-CH₃ (Weakest Acid):
- Bond Strength: The H-C bond is very strong.
- Conjugate Base: CH₃⁻ is highly unstable due to poor charge stabilization.
- Conclusion: Weakest acid.
Summary:
The ranking is based on bond strength, electronegativity, and polarizability, with H-I being the strongest Brønsted acid and H-CH₃ the weakest.