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The hydrogen-chlorine bond in HCl is very weak and it completely dissociates in water. This qualifies HCl as a strong acid. On the other hand, the bonding in HF is relatively strong. Thus, it only partially dissociates in water and makes it a weak acid.
The more electronegative an element is, the less acidic it will be when bonded with a hydrogen. Higher acidity molecules will be more likely to give off hydrogen atoms and less electronegative elements are less likely to do so. Therefore, since CL is less electronegative than F, it is more acidic and more likely to give off a hydrogen atom.
HCl is a stronger acid than HF. Since the fluorine atom is more electronegative the attraction between H and F will be greater than H and Cl, meaning that HCl will dissociate more likely than HF, making it a stronger acid
Besides looking at the electronegativity, you can also look at the bond strengths. Since Cl has a larger atomic radius than F, the bond between HCl would be longer than the bond between HF. A longer bond means a weaker bond, so it would be easier for the H to be broken off the HCl than HF. Since it's easier to break off this H on HCl, there would be more dissociation for HCl, which makes HCl be a stronger acid.
Bond strengths is the most-correct reason that HCl is a stronger acid compared to HF. If we only consider electronegativity, we only focus on how strongly F can pull H's electron, which doesn't necessarily imply how easy it is to pull the proton off of HF.
HCl is a stronger acid than HF because Cl has a larger atomic radius than F therefore the bond between the H and Cl would be longer than in HF. This makes the bond weaker since it is longer making it easier to break the bond between HCl compared to HF. The bond will dissociate more in HCl than in HF making it a stronger acid.
Jessica Booth 4B wrote:F is more electronegative than Cl so it is less likely to give off the H+ ion. This means that HCl can disassociate easier, making it the stronger acid.
This exactly explains why, but in addition HCl is a stronger acid than HF because HCl has a longer/weaker bond between the H and Cl making it easier to donate a H+. Also as the atoms go down the periodic table their size increases causing bond lengths to increase, saying that acidity decreases down the row
HCl is a stronger acid because it is lower on the periodic table, indicating that it is less electronegative and larger. This makes it easier to dissociate, making it a stronger acid. HF for this reason is often not considered a strong acid.
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