Acids and Bases

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Acids and Bases
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Properties of Acids

• sour
• water-soluble
• conduct electricity
• react with metals to produce hydrogen gas
• react with carbonates to produce carbon dioxide
  gas
• contain hydrogen (in water H ions are released)
• important in chemical industry
• corrosive

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Examples of Acids

• Vinegar (salad dressing)
• Citric acid (oranges)
• Ascorbic acid (vitamin C)
• Lactic acid (sour milk)
• Acetylsalicylic acid (Aspirin)
• Sulfuric acid (car batteries)

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Properties of Bases
A.k.a. Alkaline substances

• Bitter
• Water-soluble
• Conduct electricity
• Feel slippery
• React with proteins to break them down
• Safety hazard!

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Examples of Bases

• Sodium hydroxide (drain cleaner)
• Potassium hydroxide (soap)
• Aluminum hydroxide (antacids)
• Ammonium hydroxide (window cleaner)
• Sodium bicarbonate (baking soda)
• Potassium sulfite (preservative)

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Formulas for Acids and Bases

• Acids
• Start with H (hydrogen)
• Binary acids (HCl) vs. oxyacids (H2SO4)
• Bases
• End with OH (hydroxide)
• Also may be bicarbonate (HCO3)

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The pH Scale
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The pH Scale

• A measure of how acidic something is
• A numerical scale
• 0 really acidic, 14 really basic, 7 is neutral
• A logarithmic scale
• A change of 1 means a 10 fold increase
• Eg. A lemon (pH 2) is 100 times more acidic than
  a tomato (pH 4)
• pH -log10 H

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Applications of Acids and Bases

• Soil acidity and plant preferences
• Add lime to make soil less acidic
• Cosmetics - skin and hair products
• Basic shampoo can damage hair
• Acidic shampoo causes shine, but might not suit
  some hair types
• Acid precipitation

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Metals and Metal Oxides

• Metals react with oxygen to make metal oxides
• Metal oxides react with water to produce bases
• Therefore metal oxides are also called basic
  oxides
• K O2 ---gt K20
• K20 H20 ---gt 2KOH

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Non-metals and Non-metal Oxides

• Non-metals react in oxygen to form non- metal
  oxides
• Non-metal oxides react in water to form acids
• Therefore non-metal oxides are called acidic
  oxides
• N2 2O2 ---gt 2NO2
• 3NO2 H2O ---gt 2HNO3 NO

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Neutralization Reactions
Acid base reactions!

• HCl NaOH ---gt H2O NaCl
• Acid base reacts to form water and salt

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Titration
Determining Concentration

• Equipment
• Burette, burette clamp, retort stand
• Make sure the burette is turned off
• Put some water in the burette
• Practice controlling the flow of the water
• Put 5 mL of acid in a beaker and add 1 drop of
  phenolphthalein (phth)
• Put base in the burette (closed!!!)
• Record initial volume carefully!
• Titrate
• (add base slowly, swirling the beaker to mix
  well) until the pink JUST appears - pale pink!!!
• Record the volume used and calculate (CAVACBVB)

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Testing Antacids Lab

• Skip steps 1-4
• Step 5
• size of beaker is unimportant
• Instead of repeating steps 3 and 4
• Add 5mL of water to the measured mass of antacid
• Add 1-2 drops of phenophthalein to the antacid
• Set up your burette with acid in it like
  yesterday (20mL)
• Titrate the antacid with the HCl in your burette
  until you get it JUST BARELY clear
• 5d (replace drops of acid with mL of acid)
• Clean up
• Everything rinsed and washed out and put back
  where you got it!
• Start writing your formal lab report
• Your conclusions should use modified steps g and
  h, and UC 1 to determine which antacid is better

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Homework

• Prep for lab pg. 320
• Chapter 8 review!