Acid & Base - Physical Chemistry Presentation
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Transcript of Acid & Base - Physical Chemistry Presentation
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ACID & BASEAnnisa HayatunnufusBachelor of Pharmacy
For Subject Physical Chemistry
CONTENTA. Acid & Base (Introduction)
GENERAL DEFINITI
ON THEORIES
CHARACTERISTICS
CLASSIFICATION
DEFINITIONINDICATOR &
MEASURING TOOLS
DISSOCIATION CONSTANT
ACID & BASE EQUILIBRIUM
CONSTANT pH CALCULATION
B. pH Measure of
Acidity
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A. Acid & Base (Introduction)
?ACIDS
BASE Ionic compounds (a compound with a positive/negative charge) that break apart in water to form a hydrogen ion (H+).
Strength proportional to concentration of H+ ions in the solution.
Ionic compounds that break apart to form a negatively charged hydroxide ion (OH-) in water.
Strength proportional to concentration of Hydroxide ions (OH-).
Solutions containing bases are often called alkaline.
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A. Acid & Base (Introduction)
THEORIES
Brønsted-lowry
LewisArrhenius
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A. Acid & Base (Introduction)
CHAR
ACTE
RIST
ICS ACIDS BASES
Sour Bitter
Change color of litmus paper to red
Change color of litmus paper to blue
One of composer of many food and beverages (ie. vinegar, cheese, fruits)
In normal state present in a form of solid crystal and the strong ones are caustic
React with certain metals to produce gaseous H2
Feel slippery
React with bases to form salt & water
React with acids to form salt & water
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CLASSIFICATION
A. Acid & Base (Introduction)
ACIDS BASESFrom its origin
Organic Acid
Generally weak acids,
corrosive, and abundant in
nature
Anorganic Acid
Generally strong acids,
corrosive, and human-made
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CLASSIFICATION
A. Acid & Base (Introduction)
ACIDS BASESFrom amount of
proton given
Monoprotic
Donates only one proton or hydrogen
atom per molecule: HCl,
HNO3
Polyprotic
Donates more than
one proton or hydrogen
atom per molecule: H2S, H2SO4, H3PO4
• H2S HS- S2-
• H3PO4 H2PO4- HPO4
2- PO43-
Example:
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CLASSIFICATION
A. Acid & Base (Introduction)
ACIDS BASESFrom its strength
From its strength
Strong Acid
Completely ionized in
solution. There are only 7
strong acids: HCl, HBr, HI, H2SO4, HNO3, HClO3, HClO4
Strong Base
Completely ionized too with
only 8 members:
LiOH, NaOH, KOH, RbOH,
CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
Weak Acid
Not completely ionized in solution.
Examples are all acids aside from the ones
mentioned before.
Weak Base
Also not completely
ionized. Examples are all acids aside from the ones
mentioned before.
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CLASSIFICATION
A. Acid & Base (Introduction)
ACIDS BASESFrom its origin
Organic Acid
Generally weak acids,
corrosive, and abundant in
nature
Anorganic Acid
Generally strong acids,
corrosive, and human-made
From its strength
From its strength
Strong Acid
Completely ionized in
solution. There are only 7
strong acids: HCl, HBr, HI, H2SO4, HNO3, HClO3, HClO4
Strong Base
Completely ionized too with
only 8 members:
LiOH, NaOH, KOH, RbOH,
CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
Weak Acid
Not completely ionized in solution.
Examples are all acids aside from the ones
mentioned before.
Weak Base
Also not completely
ionized. Examples are all acids aside from the ones
mentioned before.
! Example:
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B. pH Measure of Acidity
The strength of an acid or base in an aqueous solution is measured on a scale called a pH scale.
The pH scale is a measure of the hydrogen ion concentration. It spans from 0 to 14 with the middle point (pH 7) being neutral (neither acidic or basic). Any pH number greater than 7 is considered
a base and any pH number less than 7 is considered an acid.
0 is the strongest acid and 14 is the strongest base.
pH?
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B. pH Measure of Acidity
INDICATOR & MEASURING TOOLS
Litmus Paper
Indicator Low pH color
High pH color
Hydrangeaflowers blue pink to
purpleAnthocyanins red blue
Litmus red blue
Hydrangea flower
DigitalElectronic
Universal Indicator Solution Low pH color pH range High pH color
Thymol blue (first transition) Red 1.2 – 2.8 Yellow
Methyl red Red 4.4 – 6.2 Yellow
Bromothymol blue Yellow 6.0 – 7.6 Blue
Phenolphthalein Colorless 8.3 – 10.0 Fuchsia
pH Meter
Universal Indicator
Paper
Red Cabbage
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B. pH Measure of Acidity
Dissociation Constant (Kw)Can also be known as ion product of water. Water dissociation is one of the most fundamental acid-base reaction In this reaction, water breaks apart to form a hydrogen ion (H+) and a hydroxide ion (OH-). In pure water, we can define a special equilibrium constant (Kw) as follows:
H2O H+ + OH-
KW = [H+][OH-] = 1.00x10-14
• Kw value of 1.00 x 10-14 is only applied at 25° C (unitless) and 1 atm pressure
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B. pH Measure of Acidity
The equilibrium constants (Ka & Kb)
HA + H2O → H3O+ + A– A− + H2O → HA + OH–
• The strength of an acid HA in water can be defined by the equilibrium:
• Similarly, the strength of the base A– in water is defined by the equilibrium:
How are Ka and Kb related? The answer can found by multiplying the above two
expressions for Ka and Kb:
∴ Ka Kb = Kw
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B. pH Measure of Acidity
The equilibrium constants (Ka & Kb)
HA + H2O → H3O+ + A– A− + H2O → HA + OH–
• The strength of an acid HA in water can be defined by the equilibrium:
• Similarly, the strength of the base A– in water is defined by the equilibrium:
How are Ka and Kb related? The answer can found by multiplying the above two
expressions for Ka and Kb:
∴ Ka Kb = Kw
As the strength of a series of
acids increases, the strengths of their conjugate
bases will decrease!
• Kw, Ka, & Kb are needed in calculating reactions that involve weak acid/base
(ex: buffer solutions & hydrolisis of salt)
• Buffer solutions:
• contains a weak acid (ex: CH₃COOH) together with a salt of the acid
(ex: CH₃COONa)
• used to resists a change in its pH when H+ or OH– ions are added or
removed.
• usage ex.: Blood is strongly buffered (mainly by bicarbonate) to
maintain its pH at 7.4±0.3; pH values below 7.0 or above 7.8 cause
death within minutes.
• Hydrolisis of Salt:
• dissolved salts that derives from weak acid & weak base may cause an
increase or decrease of pH according to the Ka & Kb value of the salt.
• when Ka > Kb, solution will be more acidic. When Ka < Kb, solution will
be more alkaline.
CUKSTAW (CUKUP TAU/ADDITIONAL) INFORMATION
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B. pH Measure of Acidity
Calculating pH
• pKb = - log (Kb)• Kb = 10-pKb
• Kb = antilog ( - pKb)
• pKa = - log (Ka)• Ka = 10-pKa • Ka = antilog ( - pKa)
• pOH = - log [OH-]• [OH-] = 10-pOH
• [OH-] = antilog ( - pOH)
• -log [H+]• [H+] = 10-pH • [H+] = antilog ( - pH)
[H+] [OH-]
KbKa
pH + pOH = 14
Content References
• Lower, Stephen. Introduction to Acid-base Chemistry. Chem1 General Chemistry Reference Text [Online] 1999. Available from: http://www3.imperial.ac.uk/library/subjectsandsupport/referencemanagement/vancouver/references [Accessed 10th November 2014]
• Bogren, Sue & Urbana Middle School Teachers. Acid, Base, and pH Tutorial. [Online]. Available from: http://lrs.ed.uiuc.edu/students/erlinger/water/background/ph.html [Accessed 10th November 2014]
• Gunawan, Ary. BAB 2. ASAM, BASA, DAN GARAM. United Science. Weblog. [Online] Available from: http://unitedscience.wordpress.com/ipa-1/bab-2-asam-basa-dan-garam/ [Accessed 10th November 2014]
• UNKOWN. Pengertian Asam Basa. Alfikimia. Weblog. [Online] Available from: http://alfikimia.wordpress.com/kelas-xi/larutan-asam-basa/a-pengertian-asam-basa/ [Accessed 10th November 2014]
• Shodor Organization. Acid-Base Chemistry. [Online]. Available from: http://www.shodor.org/unchem/basic/ab/ [Accessed 10th November 2014].
• http://depts.washington.edu/chemcrs/bulkdisk/chem142A_win07/notes_Solutions_Chapter_07.pdf [Accessed 15th November 2014]
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