Acids, Bases, and pH
Acids
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Release H+ ions – so are called proton donors
Contain H as the first element in the formula
Taste sour
Conduct electricity
Corrosive – will steadily eat away at a
substance
• Causes changes in an indicator
Bases
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Releases hydroxyl (OH)- ions – proton acceptor
Contains (OH)- as the last set of elements
Bitter taste, slippery feel
Conducts electricity
Corrosive
Causes changes in an indicator
Indicators
• Changes color in the presence of certain
substances
• Examples
– pH paper
– Litmus paper (red or blue)
– Phenolphthalein
Litmus
• In an acid, litmus paper will appear pink, in a
base, it will appear blue
pH Paper
• Has a variety of colors indicating specific pH
ranges for the material. From dark red for
acids to dark blue for bases.
Acid or Base Strength
• The more likely a compound is to release H+ or
(OH)- ions, the stronger it is.
• Even if a very strong acid or base (HCl or
NaOH) is diluted with water, so it becomes
less dangerous, it is still a strong substance.
Concentration
• The word concentration is a bit like the word
crowded.
Low
concentration
High
concentration
Dilute vs Concentrate
Concentrate
Low
concentration
High
concentration
Dilute
pH Scale
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Measures concentration of H+ ions.
pH<7 - acidic
pH>7 - basic
pH = 7 - neutral
Title, Purpose, Materials, and Safety
Title – Acid activity
Purpose – To gain experience determining the
pH of various substances using litmus paper
and pH paper.
Materials – ph Paper, Litmus Paper, forceps
Safety – 1. Do NOT touch substances in beakers
2. You must wear goggles
Procedure
1. Gather Materials
2. You will be assigned to one station, using the
forceps, dip a piece of red litmus paper into
the substance at that station. Record color.
3. Repeat with blue litmus.
4. Switch stations when told.
5. One of the stations will involve pH paper,
make sure you do not use the litmus paper at
that station.
Substance
Orange Juice
NaCl + H2O
Distilled H2O
Vinegar
Drano
Sugar + H2O
Aspirin + H2O
Tea
Lemon Juice
Ammonia
Baking Soda + H2O
H2O2
Maalox
Red Litmus Color
Blue Litmus Color
Acid or Base?