1. Chapter 5 Compounds are classified in different ways

2. 5.1 Acids & Bases p
Acids & bases are very common.
Classification is based on their chemical composition.
Acids & bases can be very dangerous!
Both can be very corrosive.
NEVER try to identify an acid or base by taste or touch!
See pages

3. pH Scale The strength is measured on the pH scale
Each decrease of 1 on the pH scale indicates 10x more acidic
Ex) pH 4 is ten times more acidic than pH 5
pH 3 is 1000X more acidic than pH6
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4. pH Indicators
The pH cannot be determined by sight. Instead, pH is measured by:
1) Chemicals called indicators (change colour based on the solution they are placed in) OR
2) By a pH meter (measures the electrical conductivity of the solution using electrical probes)
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5. Can be used for all pH levels: Litmus paper = most common indicator.
pH Indicators
Can be used for all pH levels:
Litmus paper = most common indicator.
Two colours: Blue = basic (>7) and Red = acidic (<7).
Universal indicators
contain many indicators
turn different colours at different pH values
can be in liquid form, or on paper strips
Can be used for only certain pH levels:
Bromothymol blue for pH ,
Phenolphthalein for pH
Many natural sources, such as beets and cabbage are also indicators
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6. Acids Chemical formula may help to identify acids.
Acids often behave like acids only when dissolved in water.
So, acids are often written with (aq) = aqueous
Chemical formula usually starts with hydrogen (H).
Acids with a carbon usually have the C written first.
Ex) HCl(aq) = hydrochloric acid
HNO3(aq) = nitric acid
CH3COOH(aq) = acetic acid
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7. Sulfuric acid is used in batteries.
Naming Acids
Sulfuric acid is used in batteries.
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Hydrogen + …-ide = Hydro…ic acid
HF(aq) = hydrogen fluoride = hydrofluoric acid
Hydrogen + …-ate = …ic acid
H2CO3(aq) = hydrogen carbonate = carbonic acid
Hydrogen + …-ite = …ous acid
H2SO3(aq) = hydrogen sulphite = sulphurous acid

8. Bases Chemical formula may help to identify bases.
Bases, like acids, often behave like bases only when dissolved in water
So, bases are often written with (aq) = aqueous
Chemical formula usually ends with hydroxide (-OH).
Bases can be gentle or very caustic
Examples of common bases
NaOH(aq)
Mg(OH)2(aq)
Ca(OH)2(aq)
NH4OH(aq)
See page 227

9. Production of Ions
See page 228
Acids & bases can conduct electricity because they release ions in solution.
Acids release hydrogen ions, H+(aq)
Bases release hydroxide ions OH–(aq)

10. pH of a solution refers to the concentration of ions it has.
Square brackets are used to signify concentration
High [H+(aq)] = low pH, very acidic
High [OH–(aq)] = high pH, very basic
A solution cannot have BOTH high [H+(aq)] & [OH–(aq)]
They cancel each other out & form water.
This process is called neutralization.
H+(aq) + OH–(aq)  H2O( )
See page 228

11. Properties of Acids and Bases
See page 229
Take the Section 5.1 Quiz