Problem 12.51 Part (a)

[Andy Liao 1B]

Problem:
Determine which acid in each of the following pairs is stronger and explain why: (a) HF or HCl; (b) HClO or HClO ; (c) HBrO2 or HClO2; (d) HClO4 or H3PO4; (e) HNO3 or HNO2; (f) H2CO3 or H2GeO3.

I was wondering why for part (a) HCl is the stronger acid. I thought that because F has a greater electronegativity than Cl, HF would be a stronger acid. Can someone please explain?

[Aijun Zhang 1D]

Actually the for acid strength: HF < HCl < HBr < HI.
HCl is a stronger acid since it is completely ionized in water while HF isn't. The bond strength of HCl is weaker than HF due to the increased radius of Cl, leading to larger distance between H and Cl than H and F. So H-Cl bond is easier to break than HF. Thus in aqueous solution, more protons are existed for HCl in the form of H3O+. So HCl is considered more stronger.
The acid constant of HF is 6.8×10^−4.

[ConnorThomas2E]

The weaker the bond strength of an Acid, the stronger it will be because it will be able to dissociate quickly and therefore create more H30. When measuring pH, since it is weaker and more easily dissociated, there will be a higher molarity in H+ ions and the pH will show that it is a stronger acid.

[Camille 4I]

How do oxygen atoms affect the strength of an acid here?