Which compound is more acidic? (without using pkA value) HCl or H2SO4

[Kaede_N9]

Homework Statement

Which compound is more acidic? (without using pkA value)

HCl or H2SO4

Homework Equations

Electronegativity.
Inductive effect.

The Attempt at a Solution

Since sulfur is more electronegative compared to cholrine, H2SO4 is more acidic than HCl...
So then I think of how I could use inductive effect instead of electronegativity to verify this claim.

Since sulfur is more electronegative compared to oxygen it shall pull away electrons slightly, more than chlorine on hydrogen?
I don't think it'll work since there are a 3 oxygens around sulfur and so the combined electronegativity outweighs that of sulfur?

What do you think?

 

[Borek]

I think I have no idea what it means to be "more acidic". And I am deadly serious, I am not aware of any definition of acidity. The way I see it it can mean one of two things - acid strength (in which case HCl is "more acidic"), or ability to neutralize base (similarly to alkalinity) - in which case H₂SO₄ as diprotic is more acidic.

Poorly worded question.

 

[Kaede_N9]

Original question:
For the following pairs of compounds, predict which one will be the strongest acid
and justify your choice.

Answer:
Between HCl and H2SO4, H2SO4 has a lower pKa (~-9) than HCl (~7) and so it is a stronger acid compared to HCl.

I wanted to answer this question without using a pKa table so I tried comparing the electronegativity of the central atoms, and as wel as their inductive effects. Not sure if inductive effect would work though.

 

[Ygggdrasil]

Also consider that resonance stabilization of the conjugate base occurs in H2SO4.

 

[Borek]

Between HCl and H2SO4, H2SO4 has a lower pKa (~-9) than HCl (~7)

Apparently it depends on the source used. Kotrly & Sucha (Handbook of Chemical Equilibria in Analytical Chemistry) list sulfuric acid pKa1 as -3, Hulanicki (Reactions of acids and bases in analytical chemistry) lists pKa of HCl as -4.