Chapter 5: Acids and Bases
ACIDS
Most acids are recognized because their formulas begin with
H. Eg. H2SO4 (sulphuric acid), HCl(aq) (hydrochloric acid).
Acids are sour tasting, water soluble and good conductors of
electricity. Many are in foods: vinegar, citrus fruits, tomatoes
When dissolved in water, acids produce hydrogen ions (H+).
Example
Hydrochloric acid  hydrogen ions + chloride ions
HCl(aq) 
H+(aq) + Cl-(aq)
Binary Acids
• When a hydrogen atom is combined with a
halogen atom and they are dissolved in water,
they form an acid.
• These acids are named by putting the name
“hydro” before the non-metal and changing the
ending to “ic” and adding “acid”.
• The four binary acids are:
Hydrochloric acid, HCl(aq)
Hydrofluoric acid, HF(aq)
Hydroiodic acid, HI(aq)
Hydrobromic acid, HBr(aq)
Oxyacids
• Oxyacids are compounds formed when hydrogen
combines with polyatomic ions that contain oxygen.
• The hydrogen atom has an ionic charge of 1+.
• Common oxyacids:
Ion Name
Ion Formula
Ionic Charge
Oxyacid Formula
Oxyacid Name
nitrate
NO 3-
1--
HNO 3(aq)
nitric acid
chlorate
ClO 3-
1-
HClO 3(aq)
chloric acid
carbonate
CO 32-
2-
H 2CO 3(aq)
carbonic acid
sulfate
SO 42-
2-
H 2SO 4(aq)
sulfuric acid
Phosphate
PO 43-
3-
H 3PO 4(aq)
phosphoric acid
BASES
• Most bases are recognized because they contain a
hydroxide ion in their formulas. Bicarbonates are also
bases.
• Bases are water soluble, bitter tasting and good
conductors of electricity. Many are in cleaning products:
soap, detergent, drain cleaner.
• The term “alkaline” may also be used to refer to a base
• When dissolved in water bases produce hydroxide ions
(OH-)
• Example:
• Sodium hydroxide  sodium ions + hydroxide ions
•
NaOH(aq)  Na+(aq) + OH-(aq)
pH scale
(page 196)
• A pH value is a measure of how acidic or basic
(alkaline) a substance is.
• The pH scale ranges from 0 to 14, where a pH
below 7 is acidic, a pH above 7 is basic and a
pH of 7 is neutral.
• A difference of one pH unit means a difference
of 10 times in acidity or basicity. So, pH value of
1 is 10 times more acidic than a pH of 2 and 100
times more acidic than a pH of 3.
Question
• Coffee has a pH of 5 and bleach has a pH
of 13.
• Which is more basic?
• How much more basic is it?
Indicators
• A pH indicator is a substance that changes
colour in the presence of an acid or base.
• An indicator can be a natural substance
such as red cabbage juice, tea, or litmus
or it can be a chemical such as
phenolphthalein or bromothymol blue.
Indicators
• Litmus
– blue in base
– red in acid
• Phenolphthalein
– colourless if pH < 8.2
– Magenta if pH > 8.2
• Bromothymol blue
– Blue in base
– Yellow in acid
Litmus
• http://lgfl.skoool.co.uk/content/keystage3/c
hemistry/pc/learningsteps/ANALC/launch.
html
Universal pH Indicator
• Page 202
• http://www.explorelearning.com/index.cfm?meth
od=cResource.dspView&ResourceID=432
Some Common Acids & Bases
(Sulfuric)
Corrosive
• BOTH strong acids (pH < 2) and strong
bases (pH > 12) are corrosive
• Stomach acid is HCl, pH of 2
• Drain cleaner is a base, pH of 14
Neutralization
• A neutralization reaction is a special case of double
displacement reaction between an acid and a base. The
products of a neutralization reaction are always water
and a salt (an ionic compound).
•
Examples:
HCl (aq)
+
NaOH(aq)  HOH + NaCl
Hydrochloric acid + sodium hydroxide  water + sodium choride
H2SO4(aq) +
2KOH

2H2O +
K2SO4
Sulfuric acid + potassium hydroxide  water + potassium sulfate
Acid-Base Chemistry in
Everyday Life
• Biology
– “Heartburn”
– Wasp & Bee Stings
• Environment
– Acid rain
– Ocean acidification
ACID REFLUX
“Heartburn”
• It’s NOT your heart, its your esophagus!
ANTACIDS
• Acid reflux can be relieved by ingesting
antacids
• These are bases that neutralize the stomach
acid
• Mild antacids are usually carbonate and
bicarbonate salts
– Eg. Alkaseltzer, Tums, Rolaids, et.
• Strong antacids are hydroxides
– Eg. “Milk of magnesia” is magnesium hydroxide
Treating Wasp & Bee Stings
• Wasp venom is basic and can be
neutralized with a weak acid like vinegar
(acetic acid)
• Bee venom is acidic and can be
neutralized with a weak base like baking
soda (sodium bicarbonate)
• http://lgfl.skoool.co.uk/content/keystage3/c
hemistry/pc/learningsteps/ENRLC/launch.
html
ACID PRECIPITATION
Effects of Acid Rain
• Aquatic – kills fish populations
• Forests – drains nutrients from the soil, leads to decreased
growth and death of trees (especially in boreal)
• Visibility – Dry acidic particles in the air lessen visibility.
• Materials – corrosion of brickwork and statues
• Human Health
– High concentrations of fine-particulate sulfate and nitrate
can enter the cardiovascular and respiratory systems,
resulting in disease or even death.
– Heavy metals, such as mercury and cadmium, from soil
deposits in lakes, streams, and reservoirs can accumulate
in the tissues of fish, making them toxic to humans.
– Metals also can be leached from the soil into reservoirs, or
from old lead and copper pipes directly into home water
supplies, causing serious illness.
Liming: adding a base to
neutralize acidified soils & water
OCEAN ACIDIFICATION
• Over 70% of the earth’s surface is covered by oceans,
making them the largest carbon sink on the planet
• Carbon dioxide reacts with seawater to make carbonic
acid, increasing the acidity of the oceans
CO2 + H2O  H2CO3(aq)
• Most life can only exist in a very narrow pH range
• Shell-bearing organisms are particularly at risk, because
the acid reacts with the calcium carbonate in the shell,
causing it to thin out. Without protection, these
organisms die more easily.
HOMEWORK
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Page 197 # 1 to 5
Page 200 # 1 & 2
Page 201 # 1 & 2
Page 203 # 1 to 4
UNIT TEST NEXT FRIDAY!