Culver City H.S.  AP Chemistry
Name____________________________
Period __ Date ___/___/___
14  Acids and Bases
STRENGTHS OF
ACIDS
List the 8 strong acids:
Overview:
There are three trends in acids that you should know and be able to explain.
 HOCl, HOBr, HOI (Note: we learned hypochlorite ion as ClO, but you also see it as OCl)
 HOCl, HClO2, HClO3, HClO4
 HF, HCl, HBr, HI or H2O, H2S, H2Se, H2Te
Background Ideas:
List the electronegativities of the following elements:
H
N
O
F
S
Cl
Br
Draw the Lewis symbol for the sulfate ion, SO42.
He
--Ne
--Ar
--Kr
---
Draw the Lewis symbol for sulfuric acid, H2SO4.
What type of bond (covalent or ionic) exists between the H and O in H2SO4? __________________
The Big Idea:
When an acid dissociates, the proton (H+) has the “choice” of sharing an electron pair with its acid or
sharing an electron pair with a passing water molecule. The less that the proton “sees” the electron pair in
the acid, the more likely that the proton will dissociate and the stronger the acid will be.
Trend #1: HOCl, HOBr, HOI
Draw the Lewis symbol for HOCl.
The more electronegative the halogen, the less the proton (H+) will “see” the electron pair.
Rank the elements, Cl, Br, and I in increasing order of electronegativity:
Rank the three acids in order of increasing strength:
Trend #2: HOCl, HClO2, HClO3, HClO4
Draw the Lewis symbols for these acids:
HOCl
HClO2
HClO3
HClO4
Which element has the lowest electronegativity value in these molecules? _____
Each oxygen atom is very electronegative and attracts electrons. In which acid will the H+ be most likely
to attach to a passing water molecule? _______
[Hint: Which acid(s) are on your strong acid list?]
Rank the four acids in order of increasing strength:
Trend #3: HF, HCl, HBr, HI
Rank the halogens in order of increasing electronegativity:
Rank the halogens in order of increasing size:
Circle the acids that are on your strong acid list:
HF
HCl
HBr
HI
Rank the acids in order of increasing strength:
Which characteristic (size or electronegativity) is more important in explaining the strength of these
acids? _______________
Consider the acids, H2O, H2S, H2Se and H2Te.
Rank these acids in order of increasing strength:
Write notes to yourself about acid strength:
 HOCl, HOBr, HOI

HOCl, HClO2, HClO3, HClO4

HF, HCl, HBr, HI or H2O, H2S, H2Se, H2Te