1. Many familiar compounds are acids or bases
5.1 - Acids and Bases
Many familiar compounds are acids or bases
Classification as acid or base is based on chemical composition
If you know a compound’s chemical formula, you may be able to identify it as an acid / base
*Acids and bases can be very dangerous*
They can be very corrosive (in the case of a strong acid) or caustic (in the case of a strong base)
NEVER try to identify an acid or base by taste or touch

2. the strength of acids & bases in measured on the pH scale
pH of an acidic solution: 1-7
the more acidic a solution, the closer its pH is to 1
pH of a neutral solution: 7
pH of a basic solution: 7-14
the more basic a solution, the closer its pH is to 14
1 unit of change on the pH scale = 10 times change in the degree of acidity / basicity
Ex. a solution with pH 4 is 101 = 10 times more acidic than a solution with pH 5
Ex. a solution with pH 3 is 103 = 1000 times more acidic than a solution with pH 6
pH of an acidic solution: 0 to < …the closer its pH is to 0
pH of a neutral solution: = 7
pH of a basic solution: > 7 to …the closer its pH is to 14
a solution with pH 3 is 103 = 1000 times more acidic than a solution with pH 6

3. litmus paper: blue = basic red = acidic
pH Indicators
pH indicators are chemicals that change colour depending on the acidity / basicity of the solution in which they are placed
litmus paper: blue = basic red = acidic
Why should you use both blue and red litmus when testing a solution?
A pH meter uses probes to measure the electrical conductivity of a solution
Indicators change colour at different pH values, so different indicators are used to identify different pH values
bromothymol blue for pH 6 – 7.6
phenolphthalein for pH 8.2 – 10
many natural sources (ie. beets and cabbage) are indicators
The blue paper changes color to red, indicating acidity somewhere between the pH range of 4.5 to 8.3 (however, note 8.3 is alkaline). Red litmus paper can indicate alkalinity with a color change to blue. In general, litmus paper is red below pH of 4.5 and blue above a pH of 8.3.
Red paper that does not change color indicates the sample is an acid. Blue paper that does not change color indicates the sample is a base.
If the paper turns purple, this indicates the pH is near neutral.

4. The chemical formula of an acid usually starts with hydrogen (H-)
Acids
Acids are often written with subscript (aq) = aqueous, since they often must be dissolved in water to behave like acids
The chemical formula of an acid usually starts with hydrogen (H-)
HCl(aq) = hydrochloric acid, HNO3(aq) = nitric acid
Acids with a carbon usually have the C written first
CH3COOH(aq) = acetic acid
"ate" means there is more oxygen in the anion than one ending in "ite"
Examples: sulfate (SO42-) has more oxygen than sulfite (SO32-), nitrate (NO3-) has more oxygen in the anion than nitrite (NO2-)

5. -ate  -ic -ite  -ous 1. hydrogen + _____-ide = hydro_____-ic acid
Naming Acids
-ate  -ic -ite  -ous
1. hydrogen + _____-ide = hydro_____-ic acid
HF = hydrogen fluoride  if no state of matter is given, start name with “hydrogen”
HF(aq) = hydrofluoric acid
2. hydrogen + _____-ate = ________-ic acid
H2CO3 = hydrogen carbonate
H2CO3(aq) = carbonic acid
3. hydrogen + _____-ite = _______-ous acid
H2SO3 = hydrogen sulphite
H2SO3(aq) = sulphurous acid
"ate" means there is more oxygen in the anion than one ending in "ite"
Examples: sulfate (SO42-) has more oxygen than sulfite (SO32-), nitrate (NO3-) has more oxygen in the anion than nitrite (NO2-)

6. HCl hydrogen chloride HCl (aq) hydrochloric acid HBr hydrogen bromide
Naming Acids – Note how the names can change with the addition of (aq).
Formula
Chemical Name
Formula in Solution
Chemical Name can be changed to...
HCl
hydrogen chloride
HCl (aq)
hydrochloric acid
HBr
hydrogen bromide
HBr (aq)
hydrobromic acid
HClO3
hydrogen chlorate
HClO3 (aq)
chloric acid
HClO2
hydrogen chlorite
HClO2 (aq)
chlorous acid
perchloric acid, has 1 more O atom in the anion than chloric acid
hypochlorous acid, has 1 less O atom in the anion than chlorous acid

7. H2SO4 (aq) - _________________________
Some “Common” Acids
HNO3 (aq) – nitric acid
H2SO4 (aq) - _________________________
H3PO4 (aq) - _________________________
H2CO3 (aq) - _________________________
Knowing these acids can help you recall the combining capacities of their polyatomic ions - YAY!!
Use the reverse cross rule and the fact that the hydrogen ion has an ion charge of +1.
sulphuric acid
phosphoric acid
carbonic acid

8. The chemical formula of a base usually ends with hydroxide (-OH)
Bases
Bases are often written with subscript (aq) = aqueous, since they often must be dissolved in water to behave like bases
The chemical formula of a base usually ends with hydroxide (-OH)
Examples of common bases
NaOH(aq)
Mg(OH)2(aq)
Ca(OH)2(aq)
NH4OH(aq)
NaOH(aq) = sodium hydroxide
Mg(OH)2(aq) = magnesium hydroxide
Ca(OH)2(aq) = calcium hydroxide
NH4OH(aq) = ammonium hydroxide
See page 227
(c) McGraw Hill Ryerson 2007

9. Production of Ions
Acids and bases can conduct electricity because they release ions in solution.
Acids release H+(aq) ions
Bases release OH–(aq) ions
The pH of a solution refers to the concentration of ions it has.
Square brackets signify concentration: [H+(aq)], [OH–(aq)]
High [H+(aq)] = low pH, very acidic
High [OH–(aq)] = high pH, very basic
H+ and OH– ions readily react with each other, so a solution cannot be both acidic and basic at the same time. They cancel each other out and form water in a process called neutralization.
H+(aq) + OH–(aq)  H2O( )
See page 228
(c) McGraw Hill Ryerson 2007

10. we sometimes use the terms “basic” and “alkaline” interchangeably
Basic = “alkaline”
we sometimes use the terms “basic” and “alkaline” interchangeably
alkaline earth metals (ie. Ca, Mg, …) combine with water to produce basic solutions…
Ex. Ca + 2H2O Ca(OH)2 + H2
(-OH) signifies
a base
See page 227
(c) McGraw Hill Ryerson 2007

11. feel** slippery (**never touch chemicals with your bare skin!)
Properties of Bases
taste* bitter (*never put anything from the science lab in your mouth!)
feel** slippery (**never touch chemicals with your bare skin!)
many bases are caustic – burn skin
no reaction with metal
conduct electricity
have a pH greater than 7
turn red litmus paper blue
phenolphthalein is pink in a basic solution
form OH-(aq) (hydroxide) ions in solution
chemical formula of a base usually ends with OH

12. taste* sour (*never put anything from the science lab in your mouth!)
Properties of Acids
taste* sour (*never put anything from the science lab in your mouth!)
many acids are corrosive – burn skin** & “eat through” metal (**never touch chemicals with your bare skin!)
conduct electricity
have a pH less than 7
turn blue litmus paper red
phenolphthalein is colourless in an acidic solution
form H+(aq) (hydrogen) ions in solution
chemical formula of an acid usually starts with H