Acids and bases can be classified based on their strength. Strong acids and bases fully dissociate in solution, while weak acids and bases only partially dissociate. The strength of an acid or base depends on factors like the polarity and stability of the conjugate ions. Acid-base reactions involve the transfer of protons between substances. The pH scale quantifies the concentration of hydrogen ions in a solution, relating acidity to the logarithm of the hydrogen ion concentration. Salts are formed by the neutralization of acids and bases.
THIS PPT WILL EXPLAIN YOU ALL ABOUT ACID AND BASE AND THEORIES OF ACID AND BASE . THIS IS VERY HELPFUL FOR THE STUDENTS FROM DIPLOMA AND BACHELOR PHARMACY STUDENTS.
This is a summary of the topic "Acids and bases" in the GCE O levels subject: Chemistry. Students taking either the combined science (chemistry/physics) or pure chemistry will find this useful. These slides are prepared according to the learning outcomes required by the examinations board.
In chemistry, acids and bases have been defined differently by three sets of theories. One is the Arrhenius definition, which revolves around the idea that acids are substances that ionize (break off) in an aqueous solution to produce hydrogen (H+) ions while bases produce hydroxide (OH-) ions in solution.
Describe in this slide the four theories of acid and base.1) Traditional theory 2) arrhenius theory 3) bronsted and lowry theory 4) lewis theory. also explained neutalisation reaction and amphoteric reactions.
THIS PPT WILL EXPLAIN YOU ALL ABOUT ACID AND BASE AND THEORIES OF ACID AND BASE . THIS IS VERY HELPFUL FOR THE STUDENTS FROM DIPLOMA AND BACHELOR PHARMACY STUDENTS.
This is a summary of the topic "Acids and bases" in the GCE O levels subject: Chemistry. Students taking either the combined science (chemistry/physics) or pure chemistry will find this useful. These slides are prepared according to the learning outcomes required by the examinations board.
In chemistry, acids and bases have been defined differently by three sets of theories. One is the Arrhenius definition, which revolves around the idea that acids are substances that ionize (break off) in an aqueous solution to produce hydrogen (H+) ions while bases produce hydroxide (OH-) ions in solution.
Describe in this slide the four theories of acid and base.1) Traditional theory 2) arrhenius theory 3) bronsted and lowry theory 4) lewis theory. also explained neutalisation reaction and amphoteric reactions.
Acids and bases buffers ARRHENIUS CONCEPT
THE LEWIS CONCEPT-THE ELECTRON DONOR ACCEPTOR SYSTEM
BRONSTED-LOWRY CONCEPT (PROTON TRANSFER
THEORY
buffer action
ph scale
buffer capacity
acid base balance
isotonicity method
isotonic soltions
buffer solutions in pharmaceutical preparations
Introduction
History
Acid & Base
Ionization of water
Definitions of pH
(1) Mathematical Definition
(2) pH
(3) pOH
Buffer solution
(1) Types
(2) Buffer action
(3) Biological buffer systems
Henderson – Hasselbalch Equation
Measurement of pH
(1) pH Scale
(2) pH indicators
(3) pH meter
pH in human body and nature
Importance
Conclusion
Reference
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.
Acid and base
1. AcidsAcids andand BasesBases
17 Acid and Base 1
A group of chemical properties is related to acidity. According to these
properties, a substance can be called an acid or a base.
The word acid comes from Latin acere meaning sour. A base is an
alkaline, which is derived from Arabic alqali.
Presence of acids and bases have been recognized by ancient people.
Lavoisier named oxygen as the element from which acids are derived.
Liebig (German) proposed that an acid contains hydrogen.
Many chemical reactions are called acid-base reactions; they are not
necessarily neutralizations.
The acid-base concept is interesting, especially the way it evolved.
Understand acid or base, important properties of substances.
2. Answer these questions
17 Acid and Base 2
What are acids?
What are bases?
What are acid-base reactions?
What are neutralization reactions?
What are the relationships between acids and bases?
What is the role of the solvent in acid or base solutions?
How does the acid-base concept evolve and why?
What are Arrhenius acid, Bronsted-Lowry acid and Lewis acids?
What is the relationship between conjugate acids and bases?
What does pH mean and how is the pH scale related to acidity?
What are salts?
Understand important properties of substances
3. Arrhenius acids and bases
17 Acid and Base 3
The fundamental concept: (Text PHH: 17-1)
Acid - any substance which delivers hydrogen ion (H+
) to the solution.
HA → H+
+ A¯
Base - any substance which delivers hydroxide ion (OH¯) to the
solution. BOH → X+
+ OH¯
Sevante Arrhenius proposed that substances exists as ions in solution in
his dissertation, which was awarded a fourth class (D) in 1884. He was
unable to find a job in his native Sweden.
He was awarded the Nobel Prize in 1903 for his electrolytic
dissociation theory.
4. Problems with Arrhenius
theory
17 Acid and Base 4
Like Dalton’s atomic theory, Arrhenius theory have problems today:
Acidity did not show in other solvent. What is the solvent role?
Some salts produce acidic or basic solutions, not neutral. Why?
Which is the base, NH3 or NH4OH? Is OH¯ really the only base?
How can H+
be stable? Are proton donated?
Some chemists want students to learn Brønsted-Lowry theory of acids and
bases before learning Arrhenius theory, because the former is more general.
Question the established theory.
5. Brønsted-Lowry theory of acids and bases
17 Acid and Base 5
An acid is a substance from which a proton can be removed.
Acids are proton donors.
A base is a substance that can remove a proton from an acid.
Bases are proton acceptors.
Because of strong desire for protons, bases rip protons off acids.
Acid-base reactions are competitions for protons.
HCl + H2
O ↔ H3
O+
+ Cl¯
HNO3
+ H2
O ↔ H3
O+
+ NO3
¯
HC2
H3
O2
+ H2
O ↔ H3
O+
+ C2
H3
O2
¯
H2
O + NH3
↔ NH4
+
+ OH¯
conjugate acids and bases
17–2
6. Problems with B-L theory
17 Acid and Base 6
The theory works very nicely in all protic solvent, but fails to
explain acid-base behavior in aprotic solvents and non-solvent
situations.
A more general concept on acid and base was proposed by G.N.
Lewis at about the same time Bronsted-Lowry theory was proposed.
Question the established theory.
7. Evolution of the acid-base
concept
17 Acid and Base 7
year thinker Acid Base acid-base reaction
1884 Arrhenius ionize ionize H+
+ OH¯ = HOH
H+
OH¯
1923 Bronsted- Proton proton HA + B = HB + A
Lowry Donor acceptor conjugation
1923 Lewis electrophil nucleophil E + Nu = E:Nu
8. Lewis acids and bases
17 Acid and Base 8
Gilbert Newton Lewis (1875-1946) influential
American chemist. His theories include the Lewis
dot structure taught in Chem120 and covalent bond
theories.
Lewis acids are electrophils: H+
, Na+
, BF3,
Lewis bases are nucleophils: NH3, H2O, PH3
Acid base reactions:
BF3 + :NH3 → F3B:NH3
Lewis at his desk.
He generalized an idea.
17–9
9. Relative strengths of
acids and bases
17 Acid and Base 9
HClO4 ClO4 ¯
H2SO4 HSO4¯
HI I¯
HBr Br¯
HCl Cl¯
HNO3 NO3¯
H3O+ H2O
HSO4¯ SO4
2
¯
H2SO3 HSO3 ¯
H3PO4 H2PO4 ¯ HNO2
NO2¯
HF F ¯
HC2H3O2 C2H3O2 ¯
Al(H2O)6
3+
Al(OH)(H2O)5
2+
H2CO3 HCO3 ¯
H2S HS ¯
HClO ClO¯
HBrO BrO¯
NH4
+
NH3
HCN CN ¯
HCO3¯ CO3
2
¯
H2O2 HO2
HS ¯ S2
¯
H2O OH¯
ROH RO¯
17–4 & 17–5 Table 17–3
The stronger the acid, the weaker
its conjugate base.
10. Skills regarding strength of
acids
17 Acid and Base 10
What are strong acids?
What are strong bases?
Which is the strongest acid, HF, HCl, HBr, or HI?
How about HNO3 and HNO2? H2SO4, H2SO3?
How about HClO4, HClO3, HClO2, HClO, and HCl?
What is the strongest acid in an aqueous solution?
What is leveling effect?
Order a given list according to the strength.
Interpret reactions as due to strength of acids and bases.
Explain strength with related acids and bases.
11. Molecular structure and acid
strength
17 Acid and Base 11
A strong acid loses its proton easily. A strong base holds onto a proton
tightly.
The more polarized is the
H—X
bond in an acid, the easier the molecule releases H+
thus a stronger
acid.
The weaker the H —X bond, the easier the molecule releases H+
thus a
stronger acid.
The bond strength and the polarity are related to electronegativity and
electrostatic interactions – size of the ions.
17–8
Able to predict acidity from molecular structure.
12. Self-ionization of water
17 Acid and Base 12
Water molecules autoionize
2 H2O (l) = H3O+
(aq) + OH¯ (aq)
[H3O+
] [OH¯]
Kc = ————————
[H2O] (= 1000/18 = 55.6)
Kw = [H2O] Kc = 1e–14 only at 25o
C, it’s T dependent.
The ion product, Kw increases as T increases, and its value remains the
same in the presence of acid or base.
17 – 3
The molecule of life, H2O, and its acidity.
13. Solutions of strong acids and bases
17 Acid and Base 13
Strong acids and strong bases completely ionize in their solutions.
HCl (aq) + H2O (l) → H3O+
(aq)+ Cl–
(aq)
KOH (aq) → K+
(aq)+ OH–
(aq)
In a 0.100 M HCl or HNO3 solution,
[H+
] = 0.100 M
and [OH–
] = 1e–14 / 0.100 = 1e–13 M at 25o
C
In a 0.100 M NaOH or KOH solution,
[OH–
] = 0.100 M
and [H+
] = 1e–14 / 0.100 = 1e–13 M at 25o
C
In a 0.010 M Ca(OH)2 solution,
[OH–
] = 2*0.010 = 0.020 M
[H+
] = 1e–14 / 0.020 = 5e–13 M at 25o
C
14. Some strong acids and bases
17 Acid and Base 14
Strong acids
Hydrogen halides
HCl HBr HI
Oxyacids of halogens
HClO3 HBrO3 HIO3
HClO4 HBrO4 HIO4
Other oxyacids
H2SO4 HNO3
Strong Bases
Hydroxides of alkali metals
NaOH KOH CsOH
Hydroxides of alkali earth
Ca(OH)2 Sr(OH)2
17 – 4
15. Neutralization Reactions
17 Acid and Base 15
The neutralization reaction between strong acids and strong bases has the
net ionic reaction
H3O+
(aq)+ OH–
(aq) = 2 H2O
The anions are bystander ions. They do not participate the reaction. These
ions are
I–
, Br–
, Cl–
, NO3
–
, HSO4
–
, CClO4
–
, Na+
, K+
, Cs+
, Ca2+
etc.
When dried, the ions left behind in neutralization reactions form salts.
16. The pH scale
17 Acid and Base 16
Sorensen introduced the pH scale in 1909 using the symbol pH
.
The p is from the German word potenz, power of (10).
pH = – log [H+
]; [H+
] = 10 –pH
pOH = – log [OH–
]; [OH–
] = 10 –pOH
pK = – log [K]; K = 10 –pK
pH = 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
[H+
] = 0.79 0.63 0.50 0.40 0.32 0.25 0.20 0.16 0.13
(not linear; need not copy, figure out yourself)
For aqueous solution;
Kw = [H+
] [OH–
]
- log Kw = pH + pOH = 14 only at 25o
C
17–3, p–672
17. pH meter and pH electrodes
17 Acid and Base 17
The pH meter is based on the principle to be
discussed in electrochemistry.
This topic is also related to the equilibrium
constant K and Gibbs free energy, ∆G.
18. Neutrality
17 Acid and Base 18
In a neutral solution, [H+
] = [OH–
]. (Different from Fig. 17-5)
In an acidic solution, [H+
] > [OH–
], and a basic solution, [H+
] < [OH–
].
In a saturated CaO (same as Ca(OH)2) solution, [OH–
] = 0.025.
Calculate pH, [H+
], [Ca2+
], and pOH at 25o
C.
Solution:
pOH = – log 0.025 = 1.60
pH = 14.00 – 1.60 = 12.40 only applicable at 25o
C
[H+
] = 10–12.40
= 4.0e–13 M Note that 4.0e-13*0.025 = 1e-14
[Ca2+
] = [OH–]
/ 2= 0.013 M
19. Answer these questions –
review
17 Acid and Base 19
What are acid-base reactions?
What are neutralization reactions?
What is the role of the solvent in acidity?
What does pH mean and how is the pH scale
related to acidity?
What are salts?
20. Acid-Base Equilibria
17 Acid and Base 20
Strong acids and bases completely ionize in their aqueous solutions.
HCl → H+
+ Cl–
KOH → K+
+ OH–
Weak acids and bases ionize but not completely in their solutions.
HCH3COO ↔ H+
+ CH3
COO–
acetic acid, vinegar spirit
HNic ↔ H+
+ Nic–
HNic = Niacine, C5NH5COOH, a water-soluble vitamin required by the
body for health, growth and reproduction; part of the vitamin B
complex. It was first prepared in pure form by oxidizing nicotine
using conc. HNO3. Nicotine is a major chemical in tobacco .
N N
CH3
N
COOH
<= Nicotine
Niacine =>
Vitamine
B3
21. Caffeine
17 Acid and Base 21
Caffeine C8H10N4O2 is a weak base,
(pH of 1% soln 6.9) taste bitter
smell like tea, a cardiac stimulant,
(boost of energy), mild diuretic,
addictive, operates using the same
mechanisms that amphetamines,
cocaine and heroin use to
stimulate the brain.
Crystals are hexagonal prisms by
sublimation, mp 238°C. Sublimes
178°. Fast sublimation is obtained
at 160-165° under
1 mm Hg pressure.
Many organic bases are interesting
drugs, and their chemistry is
fascinating.
22. Ionization of weak acids
17 Acid and Base 22
Ionization of acetic acid, HCH3COO, HA
HA = H+
+ A–
same as HA + H2O = H3O+
+ A–
[H+
] [A–
] A–
= CH3COO–
(acetate)
Ka = ————— Ka acid ionization constant, important for an acid
[HA] Ka equilibrium constant with solvent effect
The pKa is defined similar to the pH,
pKa = – log Ka Ka = 10 –pKa
See Table 17-3 on page 678
23. Some weak acids and bases
17 Acid and Base 23
Common Weak Acids
Formic acid HCOOH
Acetic acid CH3COOH
Trichloroacetic acid CCl3COOH
Hydrofluoric HF
Hydrocyanic HCN
Hydrogen sulfide H2
S
Water H2
O
Conjugate acids
of weak bases NH4
+
Common Weak Bases
ammonia NH3
trimethyl ammonia N(CH3
)3
pyridine C5
H5
N
ammonium hydroxide NH4
OH
water H2
O
HS-
ion HS-
conjugate bases of
weak acids e.g.: HCOO-
24. Determine Ka and percent ionization
17 Acid and Base 24
Nicotinic acid, HNic, is a monoprotic acid. A solution containing 0.012 M
HNic, has a pH of 3.39. What is its Ka? What is the percent of ionization?
Solution:
HNic = H+
+ Nic–
0.012-x x x
x = [H+
] = 10–3.39
= 4.1e-4
[HNic] = 0.012 – 0.00041 = 0.012
(4.1e-4)2
Ka = ————— = 1.4e-5
0.012
Degree of ionization = 0.00041 / 0.012 = 0.034 = 3.4%
25. Application of Ka
17 Acid and Base 25
The Ka of nicotinic acid, HNic, is 1.4e-5. A solution containing 0.22 M
HNic. What is its pH? What is the degree of ionization?
Solution:
HNic = H+
+ Nic–
0.22-x x x
x 2
Ka = ———— = 1.4e-5
0.22 – x (use approximation, small indeed)
x = √ (0.22*1.4e-5) = 0.0018 pH = – log (0.0018) = 2.76
Degree of ionization = 0.0018 / 0.22 = 0.0079 = 0.79%
compare with 3.4% when the solution was 0.012 M
26. pH of a weak acid
17 Acid and Base 26
The pH of C M acid HA (Ka) solution.
Method:
HA = H+
+ A–
C-x x x
x 2
Ka = ————
C – x
x 2
+ Ka x – C Ka = 0
– Ka + √Ka
2
+ 4 C Ka
x = ———————————
2
pH = – log x
The pOH of C M base BOH
(Kb) solution.
Method:
BOH = B+
+ OH–
C-y y y
y 2
Kb = ————
C – y
y 2
+ Kb x – C Kb = 0
– Kb + √Kb
2
+ 4 C Kb
y = ———————————
2
pOH = -log y
27. Using the quadratic formula
17 Acid and Base 27
The Ka of nicotinic acid, HNic, is 1.4e-5. A solution containing 0.00100 M
HNic. What is its pH? What is the degree of ionization?
Solution:
HNic = H+
+ Nic–
0.001-x x x
x2
Ka = —————— = 1.4e-5 x2
+ 1.4e-5 x – 1.4e-8 = 0
0.00100 – x
–1.4e–5 + √ (1.4e–5)2
+ 4*1.4e-8
x = —————————————————— = 0.000111 M 2
pH = – log (0.000111) = 3.95
Degree of ionization = 0.000111/ 0.001 = 0.111 = 11.1%
Deg.’f ioniz’n
0.22 0.79%
0.012 3.4 %
0.001 11.1 %
x 2
+ Ka x – C Ka = 0
– Ka + √Ka
2
+ 4 C
Ka
x = ———————————
2
28. Degree of or percent ionization
17 Acid and Base 28
Deg.’f ioniz’n
0.22 0.79%
0.012 3.4 %
0.001 11.1 %
The degree or percent of ionization of a weak
acid always decreases as its concentration
increases, as shown from the table given
earlier.
Concentration of acid
% ionization
29. Polyprotic acids
17 Acid and Base 29
Polyprotic acids such as sulfuric and carbonic acids have more than one
hydrogen to donate.
H2SO4 = H+
+ HSO4
–
Ka1 very large completely ionized
HSO4
–
= H+
+ SO4
2–
Ka2 = 0.012
H2CO3 = H+
+ HCO3
–
Ka1 = 4.3e-7
HCO3
–
= H+
+ CO3
2–
Ka2 = 4.8e-11
Ascorbic acid (vitamin C)
is a diprotic acid, abundant
in citrus fruit.
Others:
H2S, H2SO3, H3PO4, H2C2O4 (oxalic acid) …
C
30. Aspartame -
nutrasweet
17 Acid and Base 30
A dipeptide methyl ester :
L-aspartyl-L-phenylalanine methyl ester
C14H18N2O5 (molar mass = 294.31)
Aspartame has two ionizable protons
1965. Jim Schlatter
synthesized it and
discovered it sweet
31. Species concentrations of diprotic acids
17 Acid and Base 31
Evaluate concentrations of species in a 0.10 M H2SO4 solution.
Solution:
H2SO4 = H+
+ HSO4
–
completely ionized
(0.1–0.1) 0.10+y 0.10-y
HSO4
–
= H+
+ SO4
2–
Ka2 = 0.012
0.10–y 0.10+yy Assume y = [SO4
2–
]
(0.10+y) y
————— = 0.012
(0.10-y)
[SO4
2–
] = y = 0.01M
[H+] = 0.10 + 0.01 = 0.11 M;
[HSO4
–
] = 0.10-0.01 = 0.09 M
Y2
+ 0.112 y – 0.0012 = 0
- 0.112+√0.1122
+ + 4*0.0012
y = —————————————— = 0.0098
2
If concentration’f H2SO4 = 1.0 M,
what doUdo?
32. Species concentrations of weak diprotic acids
17 Acid and Base 32
Evaluate concentrations of species in a 0.10 M H2S solution.
Solution:
H2S = H+
+ HS–
Ka1 = 1.02e-7
(0.10–x) x+y x-y Assume x = [HS–
]
HS–
= H+
+ S2–
Ka2 = 1.0e-13
x–y x+y y Assume y = [S2–
]
(x+y) (x-y) (x+y) y
————— = 1.02e-7 ———— = 1.0e-13
(0.10-x) (x-y)
[H2S] = 0.10 – x = 0.10 M
[HS–
] = [H+
] = x ± y = 1.0e–4 M;
[S2–
] = y = 1.0e-13 M
0.1>> x >> y:
x+ y = x-y = x
x = √0.1*1.02e-7 =
1.00e-4
y = 1e-13
See Example 16.4
33. Beware of Misconceptions
17 Acid and Base 33
These equations show dynamic equilibria at the molecular level in a
system. These equations are not separate reactions, but they indicate
possible combination and dissociation in both directions.
H2S = H+
+ HS–
Ka1 = 1.02e-7
HS–
= H+
+ S2–
Ka2 = 1.0e-13
H2O = H+
+ OH-
Kw = 1e-14
H2O
H2O
H2S
HS-
H+
H+
H+
H2S
H2O
H2O H2S
OH-
OH-
OH-
S2-
OH-
S2-
S2-
H+
H2S(g)
HS-
34. Base-ionization constant
17 Acid and Base 34
For acid, HA
HA = H+
+ A–
[H+
] [A–
]
Ka = —————
[HA]
The pKa is defined similar to the pH,
pKa = – log Ka Ka = 10 –pKa
From slide 3
For a base BOH,
BOH = B+
+ OH–
[B+
] [OH–
]
Kb = ———————
[BOH]
The pKb is defined similar to pKa
pKb = – log Kb, Kb = 10–pKb
Whatever you have learned for weak
acids apply to weak bases
June 18
35. Common weak bases
17 Acid and Base 35
Substance Formula Kb
Ammonia NH3 1.8e-5
aniline C6H5NH2 4.2e-10
dimethylamine (CH3)2NH 5.1e-4
ethylamine C2H5NH2 4.7e-4
Hydrozine N2H4 1.7e-6
Hydroxylamine H2NOH 1.1e-8
methylamine CH3NH2 4.4e-4
Pyridine C5H5N 1.4e-9
Urea NH2CONH2 1.5e-14
no need to copy Table 16.2
Many drugs are salts of
weak bases, such as
Advil
Pseudoephedrine HCl
Buckley's mixture
Dextromethorphan
hydrobromide
Dristan
Traxodone HCl