Welcome to The Acid/Base chemistryweb-site
Factors Affecting Acid Strength
A) H-X Bond Polarity:
- When the molecule contains a hydrogen atom,
it will transfer a proton if the H-X bond is polarized,
and X atom is more polar than the H atom. - For ionic hydrides, the hydrogen atom carries
a negative charge, and acts as a proton acceptor.
For example: NaH.
H-(aq) + H2O
H2(g) + OH-(aq) - Nonpolar H-X bonds, produce neither acidic nor
basic aqueous solution.
For example: H-C in CH4(methane).
B) H-X Bond Strength:
C) Stability of the Conjugate Base X- :
Binary Acids, Are Compounds That Contains Hydrogen and
Just
One Other Element.
For Binary acids, acidity increases as the electronegativity
of the element X increases. While moving from left to
right in the same
row, and base strength increase
while moving from right to left .
HF is a weak acid, H2O is negligible, NH3 is a
weak base,
and CH4 has no acidic neither basic properties. in CH4,
the C-H bond is nonpolar, so CH4 doesn't show any
acidic or basic properties. And so can't form H+ + CH3-
ions,
however in NH3 , the N-H bond is polar, but the presence
of
a nonbonding pair of electrons on the N atom helps
NH3 act
as a proton acceptor, (a base).
Oxyacids
Are acids in which OH groups, and additional oxygen
atoms are bound to a central
atom.
The pair of electrons shared between X and O is
transferred to oxygen because
of the low
electronegativity of the metal atoms. Anionic
compounds containing OH- are formed.
Such compounds are sources
of OH- ions and
behave as bases.
If X is a nonmetal, a bond to oxygen is covalent.
As the electronegativity of X increases, the acidity of
the substance will increase.
* As electron density is drawn toward X, OH
bond becomes weaker and tends to lose the H+.
* The conjugate base is an anion, its stability
increases by increasing
the electronegativity of X.
Br- O- H 
BrO- + H+
From this equation, Br atom has an electronegativity
of 2.8 , which causes the electron density is shifted
towards Br atom.
The order of decreasing acidity, HClO > HBrO > HIO,
electronegativity
of Cl is 3, while that of Br is 2.8,
and that of I is 2.5.
By increasing the number of oxygen atoms attached to
X atom, which also leads
to an increase in the oxidation
number of the
central atom, the strength of the acid will
increase, by adding more electronegative
oxygen atoms,
they will pull electron density from the O-H bond, by
increasing
its polarity.
Carboxylic Acids: Acids with the formula, CH3-C(O)-OH
Acidity of carboxylic acid is due to the presence of the
second oxygen
atom, which attracts the electron density
from the OH bond, which increases its
polarity and help
increases the solubility of its conjugate base.
The conjugate base is stabilized by resonance. The acid
strength of
carboxylic acid increases, by increasing number
of electronegative atoms. CF3COOH > CH3COOH.
Acid And Base Topics
- Acid-Base identification Activity
- Acid-Base Identification activity
- Acid And Base Topics
- Acid/ Base characteristics/ Arrhenius theory.
- Acid/Base Arrhenius theory limitations.
- Bronsted-Lowry A/B theoryI.
- Bronsted-Lowry A/B theoryII.
- Lewis Acid/Base theory
- Acid And Base Topics
- Acid-Base strength I.
- Acid-Base strength II.
- A/B Strength QuestionII
- Acid/Base strength questionII
- Quiz
- Acid-Base Quiz
Pre-Classroom Activity and Experiments
- Litmus paper experiment
this experiment explores the effect of different chemicals on the color change of Litmus paper, it also shows the difference between Bronsted-lowry acid and base. - Indicator experiment
This experiment explores the effect of different chemicals on the color change of a n Acid-Base indicator.
- Acid-Base pH meter titration Experiment
this experiment explores the effect of different chemicals on the color change of Litmus paper, it also shows the difference between Bronsted-lowry acid and base. - Acid-Base Titration experiment
This experiment explores the effect of different chemicals on the color change of a n Acid-Base indicator.
Tutorials
- Acid-Base Identification Activity
- B/L Acid/BaseQuiz
- A/B
strength I Question
Prepared by EMAN SHAMS
