1 the chemistry of acids and bases chapter 16. 2 some properties of acids þ produce h + ions in...
TRANSCRIPT
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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)