Chapter%2023%20Acids,%20Bases,%20and%20Salts

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Chapter 23Acids, Bases, and Salts
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Acids

• An acid is a substance that produces hydrogen
  ions (H) when placed in water
• When acids/ ionic compounds are dissolved in
  water, the ions split apart from each other
  (dissociation)

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rksheets/acids_bases_coloring.html
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Properties of Acids

• Most acids
• Taste sour
• React w/many metals to form H2 gas
• Are corrosive (appears to eat away materials
  while reacting)
• Have a chemical formula that begins with H

Zinc Metal Hydrochloric Acid ? ?? Zn (s) 2
HCl (aq) ? Predict the type of reaction based
on the reactants! Single-Displacement Predict
the products of this reaction.
H2 (g) ZnCl2 (aq)
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-and-diseases/the-surprising-health-benefits-of-le
mons/
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Common Acids

• Citric Acid
• Found in citrus fruits
• Used as a preservative
• Lactic Acid
• Found in yogurt
• Produced by our muscles when they are overworked
• Acetic Acid (HC2H3O2)
• Vinegar
• Used as a preservative
• Carbonic Acid ( H2CO3) or Phosphoric Acid (H3PO4)
• Found in soft drinks
• Hydrochloric Acid (HCl)
• Found in our stomachs- aids in food digestion

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om/2010/02/08/sugary-soft-drinks-increase-pancreas
-cancer-risk
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Bases

• A base is a substance that produces hydroxide
  ions (OH-) when placed in water
• When bases/ ionic compounds are dissolved in
  water, the ions split apart from each other
  (dissociation)

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rksheets/acids_bases_coloring.html
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Properties of Bases

• Most bases
• Taste bitter
• Feel slippery
• Are corrosive (appears to eat away materials
  while reacting)
• Have a chemical formula that ends with OH

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dy/bitter-taste.html
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Common Bases

• Ammonia
• Cleaners and fertilizers
• Sodium hydroxide
• Used in soaps and drain cleaners
• Magnesium hydroxide
• An ingredient found in antacids

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Indicators

• Indicators are used to determine if a substance
  is an acid or a base
• An indicator changes a specific color when in the
  presence of an acid or a base
• Litmus Paper indicator made of a special filter
  paper that contains dyes extracted from lichens
  (the crusty stuff that grows in rocks)
• Blue litmus turns red in an ACID
• Red litmus turns blue in a BASE
• Why do you think its important to test an
  unknown substance with both types of litmus
  paper?

If one type of litmus paper does not change
color, that does not guarantee that the other
type of litmus paper will change color (i.e.
water)
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pH

• The pH scale can also help us classify solutions
  as acids or bases
• pH is a measure of the amount of H ions in a
  solution (potential hydrogen)
• The more H ions, the lower the pH, the more
  acidic the solution

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pH Scale

•  

7 lt pH 14
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Complete the following chart by telling whether
the pH represents an acid, base or neutral
substance. Also tell what color each type of
litmus paper will turn at that pH level.
pH Acid/Base/Neutral Color of Blue Litmus Paper Color of Red Litmus Paper
2      
8      
4      
7      
13      
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Strength vs Concentration

• When describing acids and bases, strength and
  concentration do not mean the same thing!
• Strength refers to the ability of the acid/base
  to dissociate in solution
• pH measures this
• Dissociation refers to the ability of an ionic
  compound to break apart into ions
• Concentration refers to the amount of acid/base
  dissolved in solution.
• An acid or base will have the same pH, regardless
  of how concentrated it is
• Just because you add water to dilute it, its
  still going to have the same amount of H ions,
  theyll just be spread out more

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Strong/Weak Acids Bases

• When a strong acid/base dissolves in water,
  nearly all of the acid/base molecules will
  dissociate into ions
• The greater the ability to dissociate, the more
  potential the acid or base has for being
  dangerous because there are more ions available
  to react
• When a weak acid/base dissolves in water, only a
  small fraction of the acid/base molecules
  dissociate (dissociate partially)
• With less ions in solution, there is less
  potential for danger because there are less ions
  available to react

Hydrogen
Hydrogen
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Strong/Weak Acids Examples

• Strong Acids
• 1. HCl hydrochloric acid stomach acid
• 2. H2SO4 sulfuric acid battery acid
• 3. HNO3 nitric acid
• Weak Acids
• 1. HC2H3O2 acetic acid vinegar
• 2. H3C6H5O7 citric acid citrus fruits

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Strong/Weak Bases Examples

• Strong Bases
• 1. NaOH sodium hydroxide
• 2. Any alkali or alkaline earth metal with
  OH-
• (i.e. KOH potassium hydroxide)
• Weak Bases
• 1. Al(OH)3 aluminum hydroxide often
  found in deodorants
• 2. NH4OH ammonium hydroxide (ammonia)
  used in many cleaning products

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Neutralization

• Neutralization is a chemical reaction between an
  acid and a base that takes place in a water
  solution
• When acids and bases react, the H ions from the
  acid react with the OH- ions from the base to
  form HOH (H2O - water!)
• The overall pH becomes neutral
• Many people that suffer from heartburn will take
  antacids to ease their symptoms (i.e TUMS). How
  do you think antacids work?

The stomach is acidic due to HCl and antacids are
basic. A neutralization reaction occurs!
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Salts

• The ions that are left behind after the H and
  OH- ions form water, combine to form a salt
• A salt is a compound that forms when the negative
  ions from the acid combine with the positive ions
  from the base
• Acid Base ? Water Salt
• HCl(aq) KOH(aq) ? H2O(l) KCl(aq)
• What type of reaction is a neutralization
  reaction?
• Double-Displacement
• Name the salt produced in this neutralization
  reaction.
• Potassium chloride

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Classify each of the following compounds as an
acid, base or salt.   Then indicate what color
each type of litmus paper will turn when placed
in this substance.
  Acid/Base/Salt Color of Blue Litmus Paper Color of Red Litmus Paper
NaOH      
HCl      
Ba(OH)2      
Al(NO3)3      
H2SO4