Acid Strength

[Patricia Chan 1C]

Could someone clarify how to determine acid strength? Lavelle mentioned in lecture that HF < HCl < HBr < HI; why exactly is that? Thank you!

[Brittney Hun 2C]

The weaker the bond the stronger the acid. So the element that is the most electronegative (strong bond) will have a weak acid.

[Sophia Shaka 3L]

To expand, the strength of the acid (or base) is determined by how fully it ionizes in water and how stable the anion is, so weaker bonds like in HI make good strong acids because HI readily dissociates in water into H+ and I-, and I- is a stable anion (electronegative and polarizable).

[Patricia Chan 1C]

Thank you for that clarification. How does one determine if an anion is more stable than another?

[Miriam Villarreal 1J]

When the Cl-, Br-, and I- anions are placed in water they are stable and remain in their state without pulling an H away from H20. Therefore they are known to be less electronegative (weaker bond), and a weaker bond is directly associated with a stronger acid.