Register to reply

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

by Kaede_N9
Tags: acidic, compound, h2so4
Share this thread:
Kaede_N9
#1
Mar8-12, 07:55 PM
P: 11
1. The problem statement, all variables and given/known data
Which compound is more acidic? (without using pkA value)

HCl or H2SO4


2. Relevant equations
Electronegativity.
Inductive effect.


3. 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?
Phys.Org News Partner Science news on Phys.org
An interesting glimpse into how future state-of-the-art electronics might work
Tissue regeneration using anti-inflammatory nanomolecules
C2D2 fighting corrosion
Borek
#2
Mar9-12, 01:34 AM
Admin
Borek's Avatar
P: 23,537
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
#3
Mar9-12, 07:22 AM
P: 11
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
#4
Mar9-12, 10:13 AM
Other Sci
Sci Advisor
P: 1,385
Which compound is more acidic? (without using pkA value) HCl or H2SO4

Also consider that resonance stabilization of the conjugate base occurs in H2SO4.
Borek
#5
Mar9-12, 11:26 AM
Admin
Borek's Avatar
P: 23,537
Quote Quote by Kaede_N9 View Post
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.


Register to reply

Related Discussions
A compound differs from an element in that a compound Biology, Chemistry & Other Homework 1
Why are acidic amino acid side chains acidic? Chemistry 4
Is H2SO4 a catalyst? Biology, Chemistry & Other Homework 5
H2SO4 preparation Chemistry 6