chapter 20
DESCRIPTION
Acid BasesTRANSCRIPT
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Chapter 20“Acids, and Bases ”
20.1Describing Acids and Bases
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Properties of acids
• Taste sour (don’t try this at home).• Conduct electricity.
–Can be strong or weak electrolytes in aqueous solution
• React with metals to form H2 gas.
• Change the color of indicators (blue litmus to red).
• React with bases (hydroxides) to form water and a salt.
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Acids Affect Indicators
Blue litmus paper turns red in contact with an acid.
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Acids React with Active Metals
Acids react with active metals to form salts and hydrogen gas:
HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)
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Acids React with Carbonates
2HC2H3O2 + Na2CO3
2NaC2H3O2 + H2O + CO2
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Effects of Acid Rain on Marble(calcium carbonate)
George Washington:BEFORE
George Washington:AFTER
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Acids Neutralize Bases
HCl + NaOH → NaCl + H2O
-Neutralization reactions ALWAYS produce a salt and water.
-Of course, it takes the right proportion of acid and base to produce a neutral salt
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Acids- Naming & Formulas
• Identify the anion making up the acid - if its “-ide” then put a hypo in front
and “ic” at the end. Ex. HCl hydrochloric acid
- if its an “-ite”, put a “ous” at the end. Ex. HNO2 nitrous acid
- if its an “-ate” , put an “ic” at the end. Ex. H2SO4 sufluric acid
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• To write a formula, make sure the cation ( which is H+), and the anion add up to 0
-Ex. Hydroflouric acid- has “hydro” and “ic” so its anion is flouride, fouride is -1, so formula is HF
- Ex. Phosphoric acid, has only an”ic”, so its anion is phosphate,PO4
3-
so the formula would be H3PO4
Acids- Naming & Formulas
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Sulfuric Acid – H2SO4
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
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Nitric Acid – HNO3
• Used in the production of fertilizers
• Used in the production of explosives
• Nitric acid is a volatile acid – its reactive components evaporate easily
• Stains proteins (including skin!)
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Hydrochloric Acid - HCl
• Used in the “pickling” of steel
• Used to purify magnesium from sea water
• Part of gastric juice, it aids in the digestion of proteins
• Sold commercially as “Muriatic acid”
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Phosphoric Acid – H3PO4
o A flavoring agent in sodas
o Used in the manufacture of detergents
o Used in the manufacture of fertilizers
o Not a common laboratory reagent
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Acetic Acid – HC2H3O2
Used in the manufacture of plastics
Used in making pharmaceuticals
Acetic acid is the acid present in household vinegar
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Properties of bases
• React with acids to form water and a salt.
• Taste bitter.• Feel slippery (don’t try this either).• Can be strong or weak
electrolytes in aqueous solution• Change the color of indicators
(red litmus turns blue).
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Examples of Bases
Sodium hydroxide (lye), NaOH
Potassium hydroxide, KOH Magnesium hydroxide,
Mg(OH)2
Calcium hydroxide (lime), Ca(OH)2
What do you notice about all these bases?
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Bases Affect Indicators
Red litmus paper turns blue in contact with a base.
Phenolphthalein turns purple in a base.
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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