Acids and Bases

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Acids and Bases
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What is an acid?

• Sour taste
• Turns blue litmus paper pink
• Makes a conjugate base
• Reacts with some metals to make H2 gas
• pH less than 7
• More H ions than OH-

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What is an acid?

• Conducts electricity
• Usually dissolved/diluted in H2O
• H ion donor in reactions
• Donates an H to base
• Sometimes water acts as the acid in the reaction

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What is an acid?

• Strong Acids
• Sulfuric Acid H2SO4
• Hydrobromic Acid HBr
• Hydrochloric Acid HCl
• Nitric Acid HNO3

• Make weak conjugate bases
• Ionize completely in reactions
• Reaction goes to completion (cannot go in
  reverse)
• Good conductors of electricity

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• Weak Acids
• Hydrofluoric Acid HF
• Acetic Acid HC2H3O2
• Hydrosulfuric Acid H2S
• Carbonic Acid H2CO3
• Ionize partially in reactions
• Reaction in equilibrium (can go in reverselook
  for the ?)
• Does not conduct electricity well
• Make strong conjugate bases

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What is a base?

• Bitter taste
• Slippery to touch
• Turns pink litmus paper blue
• More OH- ions than H ions
• pH greater than 7

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What is a base?

• Makes conjugate acid in reactions
• Accepts H from acid
• Conducts electricity
• Usually dissolved/diluted in H2O
• Sometimes water acts as a base in reactions

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What is a base?

• Strong Bases
• Litihium hydroxide LiOH
• Sodium hydroxide NaOH
• Potassium hydroxide KOH
• Magnesium hydroxide Mg(OH)2

• NaOH ? Na OH-
• Dissociate (dissolve) completely in water
  solutions to make metal ions and OH- ions
• Make weak conjugate acids

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• Weak Bases
• Ammonia NH3
• Aluminum hydroxide Al(OH)3
• Iron (III) hydroxide Fe(OH)3
• Partially dissociates in water solutions to make
  conjugate base and OH- ions
• CH3NH2 H2O ? CH3NH3 OH-
• Make strong conjugate acids

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What is the pH scale?

• The pH scale measures how acidic or basic a
  substance is.
• pH greater than 7 is basic
• pH less than 7 is acidic

Stomach acid
Household ammonia
Battery acid
Soft drinks
Tomatoes
Coffee
Antacid
Hair remover
Milk
Pure water
Blood
Soap/Detergent
Milk of magnesia
Oven cleaner
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Acids are classified by the number of Hydrogen
atoms

• Monoprotic acids 1 H
• HCl, HNO3
• Diprotic acids 2 H
• H2SO4 , H2CO3
• Polyprotic acids3 or more H H3PO4

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Other things to know
-- Water is amphoteric, which means it can act as
an acid or a base. It depends on what it reacts
with that decides if its an acid or a base. --
The process of giving off H ions is called
ionization.
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• The model used to identify acids/bases/c.
  acids/c. bases is called the BrØnsted-Lowry model
  of acids and bases
• Strength does not mean concentration. Just
  because an acid is strong does not mean it has a
  high molarity concentration.

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How do you calculate pH?
FORMULA pH -log H
Example 1 What is the pH of a solution with a
H of 1x10-2? pH - log (1x10-2) 2
Example 2 What is the pH of a neutral
solution? pH - log (1x10-7) 7
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How do you calculate pOH?

• pOH is the concentration of the OH- ions in a
  solution

• FORMULAS pOH -log OH-
• pH pOH 14

Example 1 Ammonia has an OH- concentration of
4.0x10-3. Calculate pOH and pH. pOH - log
(4x10-3) 2.40 pH 2.40 14 pH
14-2.40 11.60
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Acid Base Indicators
-- Chemical dyes that change colors depending on
their placement in an acidic or basic
solution. -- Some indicators may remain colorless
in certain pH ranges. -- Used in toys that change
colors when water is added.
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What are conjugate acids and bases?
-- Conjugate acid -- created when a base accepts
an H -- Conjugate base created when an acid
donates (gives away) an H -- Creates a conjugate
acid-base pair 2 substances related to each
other by donating/accepting H ions in a
reaction -- General equation for a acid-base
reaction is HX H2O ? H3O
X- So, H2O and OH- are a conjugate
acid-base pair and NH3 and NH4 are a pair as
well. EXAMPLES Identify the acid/base/c. acid/c.
base NH3 H2O ? NH4 OH- NH3 H2O ?
NH4 OH- HCN H2O ? H3O OH-
ACID
BASE
C. ACID
C. BASE
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Neutralization Reactions
-- Reaction where an acid and base react in an
aqueous solution to produce a salt and water --
The salt will be made up of a cation from the
base and an anion from the acid. EXAMPLE
Mg(OH)2 2HCl ? MgCl2 2H2O
base acid salt
water MgCl2 made up by Mg2 from base and Cl-
from acid

• More Examples
• Write the salt and water formed from HCl
  reacting with NaOH.
• HCl NaOH ? NaCl H2O
• salt water
• Write the equation and identify the acid, base,
  salt, and water formed when nitric acid reacts
  with cesium hydroxide.
• HNO3 CsOH ? CsNO3
  H2O
• acid base salt water