Predicting Stronger Acids in Acid Pairs

When determining which acid is stronger within a pair, we look at various factors to make our prediction. These factors include:

Electronegativity:

Acids with more electronegative atoms tend to be stronger, as they are better able to stabilize the negative charge that results from donating a proton.

Oxidation State:

The oxidation state of the central atom in an acid can also impact its strength. Generally, higher oxidation states lead to stronger acids.

Conjugate Base Stability:

The stability of the conjugate base formed after donating a proton can influence the strength of an acid. A more stable conjugate base indicates a stronger acid.

For example:

H₂SO₃ or H₂SeO₃:

Sulfur is more electronegative than selenium, making H₂SO₃ the stronger acid in this pair.

H₂SeO₄ or H₂SeO₃:

H₂SeO₄ is the stronger acid due to its additional oxygen atoms, leading to greater electron-withdrawing effects.

HBr or H₂S:

HBr is stronger than H₂S because of bromine's higher electronegativity.

H₂SO₄ or H₂SeO₄:

H₂SO₄ is stronger as sulfur is more electronegative than selenium.

HF or HBr:

HBr is the stronger acid because bromine is less electronegative than fluorine.

By considering these factors, we can make informed predictions about the relative strengths of acids within pairs.