Acids, Bases and Salts

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Acids, Bases and Salts
Version 1.0
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Acid Properties

• sour taste
• change the color of litmus from blue to red.
• react with
• metals such as zinc and magnesium to produce
  hydrogen gas
• hydroxide bases to produce water and an ionic
  compound (salt)
• carbonates to produce carbon dioxide.

These properties are due to the release of
hydrogen ions, H, in water solution.
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Base Properties

• bitter or caustic taste
• a slippery, soapy feeling.
• the ability to change litmus red to blue
• the ability to interact with acids

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• Uses of acids and bases
• Many of the things we eat use today are made up
  of acids and bases.
• Examples
• Sulfuric acid-car batteries,acid rain
• Hydrochloric acid-stomach acid
• Sodium hydrogen carbonate-baking soda and cooking

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• Uses of Acids/ Bases Contd.
• , DNA,the building block of life, stores genetic
  information.
• Amino acids, the building blocks of proteins.
• Found in movies Acids in Jurassic Park (DNA)
  and in Aliens (acidic blood).

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• Arrhenius Acid/Base Definition
• Svante Arrhenius was a Swedish scientist who
  lived from 1859-1927.

• In 1884 he advanced a theory of acids and bases.

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• An Arrhenius acid is a hydrogen-containing
  substance that dissociates to produce hydrogen
  ions.

HA ? H A-
Acid
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• An Arrhenius base is a hydroxide-containing
  substance that dissociates to produce hydroxide
  ions in aqueous solution.

MOH ? M(aq) OH-(aq)
Base
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An Arrhenius acid solution contains an excess of
H ions because an Arrhenius acid increases H
concentration, when dissolved in water.
An Arrhenius base solution contains an excess of
OH- ions because it increases OH- concentration,
when dissolved in water.
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• Bronsted and Lowry Definition
• J.N. Bronsted (1897-1947) was a Danish chemist
  and T. M. Lowry (1847-1936) was an English
  chemist.

• In 1923 they advanced their theory of acids and
  bases.

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A Bronsted-Lowry acid is a proton (H) donor.
A Bronsted-Lowry base is a proton (H) acceptor.
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Bronsted-Lowry Base
Bronsted-Lowry Acid
proton acceptor
proton donor
HCl (aq) H2O(l) ? H3O(aq) Cl-(aq)
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Conjugate acid-base pairs differ by a single
proton.
1. Are sulphate and sulfuric acid conjugate acid
and base of each other? Why or why not?
2. Write conjugate base of H3PO4. 3. Write
conjugate acid of NO3-
1. No, they differ by 2 protons. 2. H3PO4. 3.
HNO3
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. A strong acid has a weak conjugate base and
vice versa. List of strong Acids HCl, HNO3,
H2SO4, HI, HBr, HClO3, HClO4 List of Strong
Bases All group 1 and 2 metal hydroxides
Monoprotic Acids Have one proton that can be
donated. Ex. HCl, HNO3, H C2H3O2 Diprotic Acids
Have two protons that can be donated.
H2SO4 Polyprotic Acids Have more than two
protons that can be donated. Ex. H3PO4
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Compare the strengths of two acids in the
following reactions. What does the strength of
acid have to do with the direction in which this
reaction occurs? (Forward reaction is favored,
why?)
If strong acid will completely ionize
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• Lewis Acids and Bases
• In 1923 G. N. Lewis developed a more
  comprehensive theory of acids and bases.

• The Lewis theory deals with the way in which a
  substance with an unshared pair of electrons
  reacts in an acid-base type of reaction.

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A Lewis acid is an electron-pair acceptor.
A Lewis base is an electron-pair donor.
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Lewis Acid
Electron Pair Acceptor
Electron pair donated to H
Lewis Base
Electron Pair Donor
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In aqueous solution, the H or H3O ions are
responsible for the characteristic reactions of
acids.
Reactions of Acids
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Reaction with Bases The reaction of an acid with
a base is called a neutralization reaction. In
an aqueous solution the products are a salt and
water
HBr(aq) KOH(aq) ? KBr(aq) H2O(l)
2HNO3(aq) Ca(OH)2(aq) ? Ca(NO3)2(aq) 2H2O(l)
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The reaction of an acid with a base is called a
neutralization reaction. In an aqueous solution
the products are a salt and water
HBr(aq) KOH(aq) ? KBr(aq) H2O(l)
2HNO3(aq) Ca(OH)2(aq) ? Ca(NO3)2(aq) 2H2O(l)
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Salts can be considered compounds derived from
acids and bases. They consist of positive metal
or ammonium ions combined with nonmetal ions (OH-
and O2- excluded).
Chemists use the terms ionic compound and salt
interchangeably.
Salts are usually crystalline and have high
melting and boiling points.
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Salt Formation
The positive ion of the salt is derived from the
base.
The negative ion of the salt is derived from the
acid.
NaOH
HCl
base
acid
NaCl
salt
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Ionization of Water
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Water ionizes slightly.
hydroxide ion
hydronium ion
Water ionization equilibrium can be expressed
more simply as
Kw H3O OH- 1.0 x 10-14 mol/L (This
expression can be used to calculate H or OH-)
H3O or H OH- 1.0 x 10-7 mol/L What is
OH-, if H is 3.0 x 10-3? ( ans 3.3 X 10
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Two out of every 1 billion water molecules are
ionized.
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Introduction to pH
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The pH Scale
The pH of a solution is defined as the negative
of the common logarithm of the hydronium ion
concentration. pH -log H3O The pOH of a
solution is defined as the negative of the common
logarithm of the hydroxide ion concentration.
pOH -logOH-
H3O
1.0
1.0x10-7
1.0x10-14
Increasing acidity
Increasing basicity
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Calculation of pH
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H 1.0 X 10 -14/ OH-
H
OH-
OH- 1.0 X 10 -14/ H
pOH -log OH-
OH- 10-pOH
H 10-pH
pH -log H
pH BOX
pOH 14- pH
pOH
pH
pH 14- pOH
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pH -logH
H 1 x 10-5
when this number is exactly 1
pH 5
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The number of decimal places of a logarithm is
equal to the number of significant figures in the
original number.
pH -logH
H 2 x 10-5
when this number is between 1 and 10
one significant figure
ph 4.7
one decimal place
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What is the pH of a solution with an H of 1.0
x 10-11?
2 significant figures
pH - log(1.0 x 10-11)
pH 11.00
2 decimal places
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What is the pH of 0.002 M H2SO4?
H 2 x 10-3 pH - log(2 x 10-3) pH 2.7
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1. What is the pH of 0.003 M NaOH?
OH- 3 x 10-3 pOH - log(3 x 10-3) pOH 2.2
14.0-2.2 11.8
2. What is H, if pH is 3.4?
10 -3.4 4 X 10 -4
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The pH scale of Acidity and Basicity
15.4
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Neutralization
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Neutralization The reaction of an acid and a
base to form a salt and water.
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Titrations
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titration The process of measuring the volume of
one reagent required to react with a measured
mass or volume of another reagent.
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42.00 mL of 0.150 M NaOH solution is required to
neutralize 50.00 mL of hydrochloric acid
solution. What is the molarity of the acid
solution?
The equation for the reaction is
Calculate the liters of NaOH that react.
The unit of volume when using molarity is liters.
Calculate the moles of NaOH that react.
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42.00 mL of 0.150 M NaOH solution is required to
neutralize 50.00 mL of hydrochloric acid
solution. What is the molarity of the acid
solution?
The equation for the reaction is
The mole ratio of HCl to NaOH is 11
The moles of NaOH that react equals the moles of
HCl that react.
0.00630 mol NaOH react.
0.00630 mol HCl react.
The molarity of the HCl solution is
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Writing Net Ionic Equations
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In the un-ionized equation all compounds are
written using their molecular or formula
expressions.
In the total ionic equation all ions present in
solution are written.
(H Cl-) (K OH-) ? K Cl- H2O
In the net ionic equation only the ions that
react are written.
Ions that do not participate in a chemical
reaction are called spectator ions.
K ion does not react.
Cl- ion does not react.
H(aq) OH-(aq) ? H2O(l)