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Acids & Bases. Electrolytes vs. Nonelectrolytes. The ammeter measures the flow of electrons (current) through the circuit. If the ammeter measures a current, and the bulb glows, then the solution conducts. If the ammeter fails to measure a current, and the

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electrolytes vs nonelectrolytes
Electrolytes vs. Nonelectrolytes

The ammeter measures the flow of electrons (current)

through the circuit.

If the ammeter measures a current, and the bulb

glows, then the solution conducts.

If the ammeter fails to measure a current, and the

bulb does not glow, the solution is non-conducting.

definition of electrolytes and nonelectrolytes
Definition of Electrolytes and Nonelectrolytes

An electrolyte is:

  • A substance whose aqueous solution conducts
  • an electric current.

A nonelectrolyte is:

  • A substance whose aqueous solution does not
  • conduct an electric current.

Try to classify the following substances as

electrolytes or nonelectrolytes…

electrolytes
Electrolytes?
  • Pure water
  • Tap water
  • Sugar solution
  • Sodium chloride solution
  • Hydrochloric acid solution
  • Lactic acid solution
  • Ethyl alcohol solution
  • Pure sodium chloride
answers to electrolytes
Answers to Electrolytes

ELECTROLYTES:

NONELECTROLYTES:

  • Tap water (weak)
  • NaCl solution
  • HCl solution
  • Lactate solution (weak)
  • Pure water
  • Sugar solution
  • Ethanol solution
  • Pure NaCl

But why do some compounds conduct electricity in

solution while others do not…?

electrolytes1
Electrolytes
  • Ionization
    • Formation of ions caused by a reaction between water molecules
  • Strong
    • Large amount of ionization occurs
  • Weak
    • Small amount of ionization occurs
arrhenuis definition
Arrhenuis Definition
  • A substance that produces hydrogen ions (hydronium ions) as the only + ion when mixed with water
  • H+ = Hydrogen ion
  • H3O+ = Hydronium ion
  • The greater the # of H3O+ ions the stronger the acid and the stronger the electrolyte
strong acids vs weak acids
Strong Acids vs. Weak Acids

Strong acids are assumed to be 100% ionized in solution (good proton donors).

HCl

H2SO4

HNO3

Weak acids are usually less than 5% ionized in solution (poor proton donors).

H3PO4

HC2H3O2

Organic acids

organic acids
Organic Acids

Organic acids all contain the “carboxyl” group, sometimes several of them.

The carboxyl group is a poor proton donor, so ALL organic acids are weak acids.

examples of organic acids
Examples of Organic Acids

Citric acid in citrus fruit

Malic acid in sour apples

Deoxyribonucleic acid, DNA

Amino acids, the building blocks of protein

Lactic acid in sour milk and sore muscles

Butyric acid in rancid butter

properties of acids
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 H2
  • Acids neutralize bases
acids you should know
Acids you SHOULD know:

Strong Acids

Weak Acids

Sulfuric acid, H2SO4

Phosphoric acid, H3PO4

Hydrochloric acid, HCl

Acetic acid, HC2H3O2

Nitric acid, HNO3

sulfuric acid
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 refining

Thick clouds of sulfuric acid are a feature of the atmosphere of Venus.

(image provided by NASA)

nitric acid
Nitric Acid

Used in the production of fertilizers

Used in the production of explosives

Nitric acid is a volatile acid – its reactive componentsevaporate easily

Stains proteins (including skin!)

nitric acid1
Nitric Acid

Used in the production of fertilizers

Used in the production of explosives

Nitric acid is a volatile acid – its reactive componentsevaporate easily

Stains proteins (including skin!)

hydrochloric acid
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”

phosphoric acid
Phosphoric Acid

A flavoring agent in sodas

Used in the manufacture of detergents

Used in the manufacture of fertilizers

Not a common laboratory reagent

acetic acid
Acetic Acid

Used in the manufacture of plastics

Used in making pharmaceuticals

Acetic acid is the acid present in vinegar

acids are proton donors
Acids are Proton Donors

Monoprotic acids

Diprotic acids

Triprotic acids

H3PO4

HCl

H2SO4

HC2H3O2

H2CO3

HNO3

acids effect indicators
Acids Effect Indicators

Bluelitmus paper turnsredin contact with an acid.

acids react with active metals
Acids React with Active Metals

Acids react with active metals to form salts and hydrogen gas.

Mg + 2HCl  MgCl2 + H2(g)

Zn + 2HCl  ZnCl2 + H2(g)

Mg + H2SO4 MgSO4 + H2(g)

effects of acid rain on marble calcium carbonate
Effects of Acid Rain on Marble(calcium carbonate)

George Washington:

BEFORE

George Washington:

AFTER

arrhenuis base
Arrhenuis Base
  • A base is any Hydroxide that dissolves in water to yield hydroxide ions as the only negative ion
  • NaOH
  • KOH
  • Mg(OH)2
properties of bases
Properties of Bases
  • Bases taste bitter
  • Bases effect indicators
      • Red litmus turns blue
      • Phenolphthalein turns hot pink
  • Bases have a pH greater than 7
  • Bases are proton (hydrogen ion, H+) acceptors
  • Solutions of bases feel slippery
  • Bases neutralize acids
examples of bases
Examples of Bases

Sodium hydroxide (lye), NaOH

Potassium hydroxide, KOH

Magnesium hydroxide, Mg(OH)2

Calcium hydroxide (lime), Ca(OH)2

bases effect indicators
Bases Effect Indicators

Red litmus paper turns blue in contact with a base.

Phenolphthalein turns purple in a base.

bases neutralize acids
Bases Neutralize Acids

Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl.

2 HCl + Mg(OH)2

MgCl2 + 2 H2O

acids neutralize bases
Acids Neutralize Bases

Neutralization reactions ALWAYS produce a salt and water.

HCl + NaOH  NaCl + H2O

H2SO4 + 2NaOH  Na2SO4 + 2H2O

2HNO3 + Mg(OH)2 Mg(NO3)2 + 2H2O

self ionization of water
Self-Ionization of Water

H2O + H2O  H3O+ + OH-

Though pure water is considered a non-conductor, there is a slight, but measurable conductivity due to “self-ionization”

interpreting ph
Interpreting pH
  • The term “pH” means power of hydrogen
  • Refers to the H+ ions released by the acids to form H3O+ ions
  • The more H+ released the more H3O+ and the lower the pH and stronger the acid
  • The lower the pH the greater the power of Hydrogen
slide38
pH
  • The negative logarithm , to the base 10, of the H+ concentration
  • The log to the base 10 of a power 10 is equal to the power
  • -log [10-7] = 7
calculating ph poh
Calculating pH, pOH

pH = -log10(H3O+)

pOH = -log10(OH-)

Relationship between pH and pOH

pH + pOH = 14

Finding [H3O+], [OH-] from pH, pOH

[H3O+] = 10-pH

[OH-] = 10-pOH

k w ionization constant for water
Kw – Ionization Constant for Water

In pure water at 25 C:

[H3O+] = 1 x 10-7 mol/L

[OH-] = 1 x 10-7 mol/L

Kw is a constant at 25 C:

Kw = [H3O+][OH-]

Kw = (1 x 10-7)(1 x 10-7) = 1 x 10-14

titrations
Titrations
  • The molarity of an acid (or base) of unknown concentration can be determined by slowly combining it with a base(or acid) of known molarity(standard solution) until neutralization occurs
  • A method of determining the concentration of an acid or base by neutralizing it with a solution of known concentration
  • The end point is determined by the use of indicators. (endpoint – when the right amount of standard solution has been added and neutralization as occurred)
titration
Titration
  • Moles = Volume x Molarity
  • naVaMa = nbVbMb
  • na = # of H+ ions Ma = Molarity of acid
  • nb = # of OH- ions Mb = Molarity of base
  • Va = Volume of acid
  • Vb = Volume of base
indicators
Indicators
  • An indicator is a weak acid (or base) that changes its color in a known pH range when it gains or loses a H+ ion.
  • Phenolphthalein is a common indicator that is colorless when it is protonated (contains a H+) when it reacts with a base it loses it H+ and turns pink
measuring ph
Measuring pH
  • Phenolphthalein changes from colorless to pink at pH 7–9.
weak acid strong base titration
Weak Acid/Strong Base Titration

A solution that is

0.10 M CH3COOH

is titrated with

0.10 M NaOH

Endpoint is above pH 7

strong acid strong base titration
Strong Acid/Strong Base Titration

Endpoint is at

pH 7

A solution that is

0.10 M HCl is titrated with

0.10 M NaOH

strong acid strong base titration1
Strong Acid/Strong Base Titration

A solution that is

0.10 M NaOH is titrated with

0.10 M HCl

Endpoint is at

pH 7

It is important to recognize that titration curves are not always increasing from left to right.

strong acid weak base titration
Strong Acid/Weak Base Titration

A solution that is

0.10 M HCl is titrated with

0.10 M NH3

Endpoint is below

pH 7