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1 The Chemistry of Acids and Bases Chapter 16. 2 Some Properties of Acids þ Produce H + ions in...

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1 The Chemistry The Chemistry of Acids and of Acids and Bases Bases Chapter 16 Chapter 16
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The Chemistry The Chemistry of Acids and of Acids and BasesBases

The Chemistry The Chemistry of Acids and of Acids and BasesBases

Chapter 16Chapter 16

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Some Properties of Acids

Produce H+ ions in water

Taste sour

Corrode metals

Electrolytes

React with bases to form a salt and water

pH is less than 7

Turns blue litmus paper to red “Blue to Red A-CID”

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Some Properties of Bases

Produce OH- ions in water

Taste bitter, chalky

Are electrolytes

Feel soapy, slippery

React with acids to form salts and water

pH greater than 7

Turns red litmus paper to blue “Basic Blue”

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Strong Acids and Strong Bases

ACIDS

HCl

HBr

HI

HNO3

H2SO4

HClO3

HClO4

BASES

LiOH

NaOH

KOH

RbOH

CsOH

Sr(OH)2

Ba(OH)2

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Arrhenius acid is a substance that produces H+ in water

Arrhenius base is a substance that produces OH- in water

HCl H+ + Cl-

NaOH Na+ + OH-

Acid/Base theories

#1: The Arrhenius theory – describes acids and bases by the type of ion each produces in water

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Acid/Base theories

#2: Brønsted – Lowry – describes acids and bases in terms of protons

Acids – proton donor

Bases – proton acceptor

A “proton” is really just a hydrogen atom that has lost its electron!

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The Brønsted – Lowry Theory

• When an acid dissolves in water the hydrogen ion leaves the acid and bonds to the water molecule, forming hydronium ion (H3O+)

HCl + H2O H3O+ + Cl-

• When a base dissolves in water, a hydrogen leaves from water and bonds to the base, leaving hydroxide ion (OH-)

NH3 + H2O ↔ NH4+ + OH-

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Conjugate Acids and Bases(part of the Brønsted – Lowry Theory)

• Conjugate Acid- is the species produced when a base accepts a hydrogen ion from an acid.

• Conjugate Base- is a species that results when an acid donates a hydrogen ion to form a base.

• Conjugate Acid-Base Pair- consists of two substances related to each other by the donating and accepting of a single hydrogen ion.

• Amphoteric- water and other substances that can act as both an acid and a base

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Conjugate Pairs

HC2H3O2 + H2O C2H3O2- + H3O+

Acid Base Conj. Base Conj. Acid

How to identify conjugate acid – base pairs:•An acid’s formula begins with an ionizable hydrogen (HA)

•Its conjugate base is the particle formed after the hydrogen ion leaves (A-)

•A base accepts the hydrogen ion from the acid

•Its conjugate acid is the particle formed after the hydrogen ion is added

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Try to identify acid, base, conjugate acid and conjugate

base

• NH4+(aq) + OH-(aq) NH3(aq) + H2O (l)

• CH3NH2 + H2O CH3NH3+ + OH-

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pH• The pH of a solution is a measure of the

hydronium ion concentration in that solution

• The formula for calculating pH is:

pH = -log [H3O+]

*** For ALL strong acids, the hydronium ion concentration is equal to the concentration of the acid given in the problem

• To calculate the pH of a strong base, use this formula:

pH = 14.00 – (-log[OH-])

*** For ALL strong bases, the hydroxide ion concentration is equal to the concentration of the base given in the problem

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pH of salts

• Consult the following chart to determine whether a salt is acidic, basic or neutral

• For example KBr is neutral, because KOH and HBr are both strong, but NaF is basic because NaOH is strong and HF is weak

If the cation is from a…

And the anion is from a…

The salt is…

Strong base Strong acid Neutral (pH = 7.0)

Strong base Weak acid Basic (pH > 7.0)

Weak base Strong acid Acidic (pH < 7.0)


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