Chemistry Acids and Bases Properties and pH Chemical Warfare What is an Acid 3 Major Definitions Arrhenius BronstedLowry and Lewis Arrhenius and BronstedLowry say an acid is A proton donor ID: 266404
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Slide1
Acids and Bases and pHSlide2
Chemistry
Acids and Bases
Properties and pHSlide3
Chemical Warfare!Slide4
What is an Acid?
3 Major Definitions: Arrhenius, Bronsted-Lowry, and Lewis.
Arrhenius and Bronsted-Lowry say an acid is:A proton donorWhat is a proton?A proton = H+H + = H3O +Slide5
Acid and Base Strength
Acids and bases are considered “strong” or “weak” depending on how much they dissociate
The more something dissociate, the stronger acid or base it is.This means we are looking at the amount of H+ or OH- is in the solutionSlide6
Ionization of HCl and formation of hydronium ion, H
3
O
+
H
2
O + HCl
H
3
O
+
+ Cl
-
Proton
donor
Proton
acceptorSlide7
Strong Acids vs. Weak Acids
Strong acids are assumed to be 100% disassociated in solution (good proton donors).
Are Strong Electrolytes
Weak acids are usually less than 5% disassociated in solution (poor proton donors).
Are Weak Electrolytes.
HCl
H
2
SO
4
HNO
3
H
3
PO
4
HC
2
H
3
O
2Slide8
Strong Acid DissociationSlide9
Weak Acid DissociationSlide10
Arrhenius & Bronsted-Lowry Acids=
Proton Donors
Mono
protic acids
Di
protic acids
Tri
protic acids
H
Cl
H
C
2
H
3
O
2
H
NO
3
H
2
SO
4
H
2
CO
3
H
3
PO
4Slide11
Properties of Acids
Acids taste sour
Acids effect indicators
Blue litmus turns red
Methyl orange turns red
Acids have a pH lower than 7
Acids are proton (hydrogen ion, H
+
) donors
Acids react with active metals, produce H
2
Acids react with carbonates, produce CO
2
Acids neutralize basesSlide12
Sulfuric Acid
Highest volume production of any chemical in the U.S.
Used in the production of paper
Used in production of fertilizers
Used in petroleum refiningSlide13
Nitric Acid
Used in the production of fertilizers
Used in the production of explosives
Nitric acid is a volatile acid – its reactive components evaporate easily
Stains proteins (including skin!)Slide14
Hydrochloric Acid
Used in the pickling of steel
Used to purify magnesium from sea water
Part of gastric juice, it aids in the digestion of protein
Sold commercially as
“
Muriatic acid
”Slide15
Phosphoric Acid
A flavoring agent in sodas
Used in the manufacture of detergents
Used in the manufacture of fertilizers
Not
a common laboratory reagentSlide16
Acetic Acid
Used in the manufacture of plastics
Used in making pharmaceuticals
Acetic acid is the acid present in vinegarSlide17
Acids Effect Indicators
Blue litmus paper turns red in contact with an acid.Slide18
Acids Have a pH less than 7Slide19
Acids React with Active Metals
Acids react with active metals to form salts and hydrogen gas.
Mg + 2HCl
MgCl
2
+ H
2
(g)
Acids did not react with Copper, because copper is not an
“
Active Metal
”Slide20
Acids React with Carbonates
2HC
2
H
3
O
2
+ Na
2
CO
3
2 NaC
2
H
3
O
2
+ H
2O + CO2Slide21
Effects of Acid Rain on Marble
(calcium
carbonate
)
George Washington:
BEFORE
George Washington:
AFTERSlide22
What is a Base?
3 Major Definitions: Arrhenius, Bronsted-Lowry, and Lewis.
Arrhenius Base increases OH- concentration when in solution.NaOH when disassociated produces:Na+ & OH
-Bronsted-Lowry Bases are proton (H+) acceptors.NH3 + HCl
NH
4
+
+ Cl
-
An Arrhenius base is always a B-L Base, but a B-L base is not always an Arrhenius base.Slide23
Properties of Bases
Bases taste bitter
Bases effect indicators
Red litmus turns blue
Phenolphthalein turns purple
Bases have a pH greater than 7
Bases are proton (hydrogen ion, H
+
) acceptors
Solutions of bases feel slippery
Bases neutralize acidsSlide24
Examples of Bases
Sodium hydroxide (lye), NaOH
Potassium hydroxide, KOH
Magnesium hydroxide, Mg(OH)
2
Calcium hydroxide (lime), Ca(OH)
2Slide25
Strong Bases vs. Weak Bases
Strong bases are assumed to be 100% disassociated in solution.
Are strong electrolytes!
Weak acids are usually less than 5% disassociated in solution.
Are Weak electrolytes!
NaOH
Ca(OH)
2
Cu(OH)
2
NH
3Slide26
Strong Base Dissociation
NaOH
Na
+
OH
-Slide27
Weak Acid Dissociation
OH
-
AgOH
Ag
+
AgOHSlide28
Bases Effect Indicators
Red litmus paper turns blue in contact with a base.
Phenolphthalein turns purple in a base.Slide29
Bases have a pH greater than 7Slide30
Is H2O an acid or base?
HCl +
H2O H3O+ + Cl-
H2O is an base! = proton acceptorNH3
+ H
2
O NH
4
+
+ OH
-
H
2
O is an acid! = proton donor
H
2O can be either. This is calledAmphoteric = can act like an acid or base.Slide31
Ion Concentration in WaterSlide32
pH- what is it?
pH is a measure of the H
+ or H3O+ concentration.The higher the concentration of H+ or H3O+ , the lower the pH.Acids have higher [H3O+
], than pure waterpH range of an acid is 0 - 6.99.pH of pure water is 7Slide33
pOH- what is it?
pOH is a measure of the OH
- concentration.The higher the OH- concentration, the lower pOH.Bases have higher OH- concentrations than pure water.pH and pOH are exact opposites!In a solution:
when the [H3O+] increases, [OH-] decreases when pH increases, pOH decreasesSlide34
Self-Ionization of Water
H
2
O + H
2
O
H
3
O
+
+ OH
-
pH explainedSlide35
H+, OH-, and pHSlide36
pH ScaleSlide37
How Do You Determine?
Described
by an ionization equation:Each acid and base will have either a high or low percent ionizationi.e. a high or low amount
of the solution which dissociates into ionsThe higher the percent ionization the stronger the acid
HCl
(
aq
)→ [H]
+
+ [
Cl
]
–Slide38
pH
The
pH is defined according to the following formula:pH = -log[H+]and [H
+]=10-pHwhere [H+] represents the concentration of hydrogen ions in
mol
/L Slide39
pOH
The
pOH is defined according to the following formula:pOH = -log[OH-]and [OH
-]=10-pOHAlso note that pH + pOH= 14Slide40
pH and pOH is logarithmic
The
pH and pOH scale is logarithmic, just like the Richter scale for earthquakes!So a change of 1 pH means the concentration has changed by a factor of 10!Slide41
Acid and Base Strength
For
bases, a solution with a pH of 13 is:10 times more basic than a solution with a pH of 12
100 times more basic than a solution with a pH of 11 For acids, a
solution with a
pH of 3
is:
10
times more acidic than a
solution
with a
pH of
4
100 times more acidic than a solution with a
pH of 5Slide42
Measuring pH with wide-range paperSlide43
Narrow-Range pH PaperSlide44
How Else Can We Measure Strength?
Scientists use a
pH scale to represent how acidic or basic a solution is
pH means "power of hydrogen”Slide45
Practice Problems
What is the pH
of a 1.2 x 10-3 HBr solution?What is the pOH of a 1.2 x 10
-3 HBr solution?Slide46
Practise Problems
What is the [H+] concentration in a solution with a pH of 7?
What is the [OH-] concentration in a solution with a pH of 12?Slide47
Indicators
The most common method to get an idea about the pH of solution is to use an acid base indicator
An indicator is a chemical that changes colour depending on the pHA variety of indicators change color at various pH levelsSlide48
Litmus paper
The most common indicator is found on "litmus" paper
It is red below pH 4.5 and blue above pH 8.2 Slide49
Phenolphthalein
Phenolphthalein is a most common liquid indicator
It is clear below pH 8.5 and pink above pH 8.5Slide50
Other Indicators
Can also
be obtained from many natural sources like strawberries, cabbage, tea and tulips Slide51
OTHER Tools
Basic indicators
only show if a substance is acidic or basic, but not strengthUniversal indicator are a mixture of indicators and can show strength of acid or baseSo can a pH Meter